Chapter 4 - Elements of Design

Elements of Design

Department Resources
Policy Implement O-06: Complete Streets Policy
Complete Streets Design Guide
Policy Implement D-07: Context Sensitive Design Policy
Engineer of Record Responsibilities
Policy Implement D-04: Engineering Plan Approval Policy
Policy Implement T-07: Safe System Approach

The project development process requires the design team to evaluate an extensive list of interrelated elements, with often competing criteria, to ensure compliance with the guidance provided within this manual and its references. A seemingly minor change can trigger a cascade of effects on other elements based on their inherent interconnection. Consequently, a project’s design must be treated as an iterative process to achieve a suitable balance while meeting all applicable requirements and obligations. This manual is not intended as a design standard or as a guidance manual; instead, this chapter has been written to summarize DelDOT’s practices and policies that will need to be considered and followed by the design team throughout the project development process.

Several overarching concepts outlined within this section should be kept in mind throughout the design process. Those concepts are as follows:

• Complete streets – DelDOT strives to maintain a comprehensive, integrated, and connected transportation network that is safe and efficient for all modes of transportation. This allows users to choose among different transportation modes, both motorized and non-motorized. DelDOT’s complete streets process was first formalized in April 2009 with Executive Order 6, which called for a statewide complete streets policy. On January 6, 2010, the DelDOT Complete Streets Policy became effective. DelDOT’s complete streets policy is contained in DelDOT Policy Implement O-06 entitled Complete Streets Policy. The policy implement describes a project’s applicability to the complete streets policy in accordance with its scope:
• All projects in the State right-of-way that are considered road reconstruction, widens the pavement width, or allows for the inclusion of facilities for all users, are to consider all transportation modes and accommodate accordingly. The facility type is to be based on the project location and the needs of the community.
• System maintenance projects are intended to keep what the State already owns in a good state of repair and are usually preservation or pavement rehabilitation projects which require limited design and no right-of-way acquisition. While it is not the specific intent of these projects to expand existing facilities, opportunities to provide and improve safety for other modes are to be explored during the project development stage.

  DelDOT also maintains a Complete Streets Design Guide which focuses on implementing complete street concepts during the project-level planning and conceptual design phase. The intent of this guide is that complete street design considerations are evaluated at the beginning of a project when they can be most readily implemented into a project’s scope.

• Future maintenance – Improvements incorporated into the transportation network will require performance of maintenance throughout the service life of the facility. Accordingly, the design team should consider future facility maintenance demands during the design phase. These considerations include prescribing materials appropriate for the intended facility service life and site access.
• Context sensitive design – DelDOT has adopted a context sensitive design policy as a method of incorporating community desires and unique site opportunities into transportation projects. DelDOT’s Context Sensitive Design policy is detailed in Policy Implement D-07 entitled Context Sensitive Design Policy. Context sensitive design is a proactive approach to planning and designing improvements to the transportation system that considers each project within the context of its site, while gathering and including information and ideas from the public throughout the planning and design process. Context sensitive design involves a collaborative, interdisciplinary approach in which citizens are part of the project team. It simultaneously advances the objectives of safety, mobility, enhancement of the natural environment, and preservation of community values.
• Engineer of Record Responsibilities – Title 24, Professions and Occupations and Title 29, State Government of the Delaware Code require the dating, signing, and sealing of various project development related deliverables. The individual who signs and/or seals the work product must be professionally licensed in the State of Delaware and is designated as the Engineer of Record. The Engineer of Record is expected to comply with all applicable engineering standards, guidelines, policies, regulations, and laws for their project. The responsibilities and obligations of the Engineer of Record are more fully described in 24 Del. C. Chap. 28. Typical Engineer of Record responsibilities on DelDOT projects are established in DelDOT’s Engineer of Record Responsibilities Memo. DelDOT’s dating, signing, and sealing policies for various deliverables are described throughout this manual and are further defined in Policy Implement D-04 entitled Engineering Plan Approval Policy. The design team must be cognizant of their responsibilities and potential liability under the Delaware Code throughout the design process.
• Safe System Approach – DelDOT takes a proactive approach to addressing the contributing factors and crash types that lead to fatal and serious crashes. Accordingly, DelDOT has adopted the Safe System Approach through Policy Implement T-07 to address and mitigate the risks inherent in the transportation network. The Safe System Approach to road safety is holistic and based on five elements: safe road users, safe vehicles, safe speeds, safe roads, and post-crash care. The Safe System Approach applies the following principles: death and serious Injuries are unacceptable, humans make mistakes, humans are vulnerable, responsibility is shared, safety is proactive, and redundancy is crucial. The Safe System Approach also establishes a Roadway Design Hierarchy to help characterize engineering and infrastructure-based countermeasures and strategies relative to their alignment with the Safe System Approach. The four tiers include: remove severe conflicts, reduce vehicle speeds, manage conflicts in time, and increase attentiveness and awareness. The Safe System Approach emphasizes the use of multiple layers of protection to both prevent crashes and to reduce harm caused to those involved when crashes occur. Additional information on the approach is included in Policy Implement T-07 entitled Safe System Approach as well as on the United States Department of Transportation’s website.

Municipalities in Delaware may have requirements that could affect the project development process. When a project is within municipal limits, the design team should proactively coordinate with municipal officials to ensure project compliance and to prevent costly delays. Additional information on this topic is provided in Section 5.2 [NEEDS LINK].

4.1 Design Standards

The design team is tasked with making numerous decisions as to the geometrics and physical characteristics of roadways that balance a mix of factors such as cost and safety as part of the design process. Balancing the mix of factors will require use of discretionary judgement throughout the design process that is oftentimes referred to as engineering judgement. Without some basic framework of design standards, the judgments of individual designers may vary considerably. The purpose of design standards is to assure that roadway improvements are consistently designed with due consideration of the design controls established in Section 4.1.1.

23 CFR 625 establishes the design standards that are acceptable to the Federal Highway Administration (FHWA) for application in geometric and structural design. The CFR incorporates AASHTO policy documents by reference and establishes flexibility for states to develop their own design standards for projects that are not on the National Highway System (NHS) and for resurfacing, restoration, and rehabilitation (3R) type projects. This allowance recognizes that there are many different project types and that design standards appropriate for new construction or major reconstruction may be impractical both economically and in level of disruption to the existing community for smaller-scale projects.

The design standards within the AASHTO policy documents have generally evolved from extensive highway agency field-testing, research, mathematical modeling, and studies over many years of application and experience. The findings and conclusions within the AASHTO policy documents are intended to serve as guides for designers with many criteria being presented as a range of acceptable values. Accordingly, the design standards are flexible in that agencies must adopt those that are proven to work best for the area(s) over which they have jurisdiction.

Providing flexibility in the application of design standards based on project type and setting is an example of context sensitive design being incorporated into the project development process. Selecting design standards that are context sensitive and that preserves scenic, aesthetic, historic, and environmental resources, while maintaining safety and mobility for all users is an important part of the design process. Elements that influence the selection of design standards include topography, geographical location, physical geology, predominant weather conditions, population growth, traffic volumes, predominant types of vehicles, past operational experiences, state and local transportation goals, and community interests.

The flexibility to select project specific design standards does not compromise the national goal of maintaining a standard design. The concept of a standard design is reached through the consistent application of design principles. Drivers can reasonably expect transportation agencies to apply the same design principle when encountering similar conditions throughout the United States allowing the driver to be prepared and react in a consistent manner. For instance, all freeway ramps will have deceleration lanes and consistent signing. The flexibility provided within AASHTO and federal policies allow the design team to select design standards that will meet user expectations while considering a project’s intent and associated funding limitations.

DelDOT uses a process of first establishing design controls which is then used to select design criteria in recognition of the importance of context sensitive design solutions. This process also encourages transparent and well documented decision-making, which is important as there are many decisions made during the design process that affect the selection of design standards.

4.1.1 Design Controls

Department Resources
Design Control Checklist
Plan Submission Checklist

A fundamental concept in the project development process is that every project is unique and that there are no generic solutions. Each project requires a design team to evaluate and address the needed improvements while integrating the design into the surrounding social, natural, and manmade environment. Establishing a project’s design controls is the foundational first step that DelDOT uses to ensure the selection of context sensitive design standards.

DelDOT’s Design Control Checklist should be completed within the project development process in accordance with a project’s type as described in Section 4.1.3. The design controls selected help define a project’s unique characteristics or features that must be considered before establishing a project’s geometric and structural standards. The Design Control Checklist should be completed as early in the project development process as feasible due to the fundamental role it serves in conceptually shaping a project. DelDOT’s Plan Submission Checklist requires the Design Control Checklist be submitted at the Preliminary Plans milestone submittal.

A project’s design controls can be separated into those related to the project’s area and surrounding community and the facility users and system demand. Design control decisions should be revisited as more detailed information is obtained and periodically throughout the project development process for re-verification purposes.

4.1.1.1 Project Area and Surrounding Community Context

The context of a project’s physical setting and surrounding community environment is instrumental in establishing a project’s unique characteristics. Elements that are to be considered as part of the design control establishment process include the following:

• Community values and resources – Understanding a community’s values is key to ensuring that a project and its goals are in harmony with the environmental, social, scenic, aesthetic, historic, natural, or constructed resources of the area. This understanding is accomplished by gathering information from the public throughout the project development process.
• Functional classification – Functional classifications are assigned to roadways based on the type of trips, mix of traffic, accessibility to the facility, and the overall role of the facility in the total transportation system. The functional classification provides key insight into a roadway’s intended function in the transportation network. Functional classifications range from interstates, which were specifically designed for long-distance travel, to local streets which are not intended for long-distance travel except for origin or destination ends of the trip. A roadway’s functional classification is available through DelDOT’s Gateway GIS dataset which is discussed in additional detail in Section 3.7.1.1 [NEEDS LINK].
• Terrain within project area – A project’s topographic characteristics are influential in setting a user’s expectations for the alignment of roads and streets and helps define the overall context of the project site.
• Access control – Evaluating a project’s level of access control provides contextual information as to how the existing facility functions. A facility’s level of access control is closely related to its functional classification.

4.1.1.2 Traffic Context

Existing and future traffic characteristics are key elements for assessing a project’s context within the transportation network. The design team should identify the different modal users which the design will need to accommodate and their volume and associated characteristics. The Division of Planning will provide existing and future traffic data in accordance with Section 3.7.3 [NEEDS LINK]. Volume and traffic data are expressed in several different ways:

• Annual Average Daily Traffic (AADT). The total yearly volume divided by the number of days in the year.
• Average Daily Traffic (ADT). The total volume during a given time period in whole days greater than one day and less than one-year divided by the number of days in that time period.
• Peak-Hour Traffic (PHT). The traffic volume during an interval shorter than a day, usually one hour, that reflects the frequently repeated rush-hour periods. On some roads, such as those serving the beach areas, traffic is significantly heavier in one season. For these roads, the design should take into consideration the ADT for the peak months.
• Design Hourly Volume (DHV). The peak hourly volume expected in the 30th highest hour during the chosen design year. This helps give a better picture of unusual seasonal fluctuations or other conditions that may cause capacity problems.
• Directional Distribution (D). A measure of the highest traffic volume in one direction during peak hours, expressed as a percentage of the DHV. This is principally important in areas with relatively high traffic volumes where system capacity is being approached.
• % Trucks. Vehicle composition should also be assessed, as vehicles of different sizes and weights have different operating characteristics, which must be considered in roadway design. Besides being heavier, large trucks generally are slower and occupy more space than passenger cars. The overall effect of one truck on traffic operations is often equivalent to several passenger cars. The volume of trucks is also a key component of the pavement design.

Existing and proposed traffic characteristics and site conditions can be used to determine an existing or proposed level-of-service (LOS) to ensure that the facility is appropriate for the characteristics of the traffic and will meet the facility user’s expectations.

4.1.2 Design Criteria

Department Resources
Design Criteria Form
Plan Submission Checklist
Road Design Manual

A project’s design criteria can be determined once the design controls are established. The Design Criteria Form is to be completed based on the project type requirements described in Section 4.1.3. A project’s Design Criteria Form is used to ensure that the geometric and structural standards have been selected consistent with DelDOT’s design policies. DelDOT’s Plan Submission Checklist requires the Design Criteria Form be submitted at the Preliminary Plans milestone submittal.

Many design decisions and the majority of a project’s design criteria are established based on a project’s selected design speed. Geometric requirements are generally less stringent with lower speeds, in difficult terrain, and in urban areas. Guidance on selecting a project’s design speed is contained within the DelDOT Road Design Manual.

A project’s variance from the selected design criteria does not always necessitate the need for the creation of a formal design exception in accordance with Section 4.1.4; however, it is a best practice to document deviations from the selected design criteria in the project file for any known project divergence from the selected design criteria. The level of documentation required is generally commensurate with the project’s type and associated scope. Supporting information could include analysis of crash records, existing roadway characteristics, required and proposed design criteria, cost analysis, compatibility of adjacent roadway sections or intersections, and proposed measures to mitigate deviations from design criteria.

As with a project’s design control decisions, a project’s design criteria decisions should be revisited as more detailed information is obtained and periodically throughout the project development process for re-verification purposes.

4.1.3 Application of Standards by Project Type

Table 4.1.3 – Required Design Documentation
Project Type	Design Control Checklist	Design Criteria Form	Design Exception
New Construction	X	X	X
Reconstruction (4R)	X	X	X
Resurfacing, Restoration, and Rehabilitation (3R) (NHS)	X	X	X
Resurfacing, Restoration, and Rehabilitation (3R) (Non-NHS)	X	X
Preventive Maintenance (1R and 2R)	+
Miscellaneous Improvement	+
“X” signifies that the design level documentation is required “+” signifies that the design level documentation is recommended

DelDOT, as well as other transportation infrastructure owners, perform a variety of projects with varying scopes to enhance and maintain their infrastructure networks. Projects can range from the creation of large facilities on new alignments to minor activities like crack sealing existing roadways. Most projects performed by DelDOT do not involve new construction or major reconstruction activities that would readily allow for incorporation of significant changes to meet the design standards intended for new construction or reconstruction projects. Accordingly, DelDOT defines several project types to assist the design team in creating context sensitive solutions to the transportation deficiencies their projects address. Additionally, DelDOT’s defined project types establish a framework for justifying design decisions regarding project scope.

The project types defined in this section are based upon the requirements in 23 CFR 625 and guidance provided in current FHWA policy memorandums. Historically, project scopes have been classified in accordance with an ‘R’ system where a project’s scope increases with each additional R added to the project type. Under this methodology, a 4R reconstruction project would have a larger scope than a 2R Restoration and Resurfacing project. Though, not as widely used as previously, the naming convention is still prevalent in current regulation and policy documents.

Table 4.1.3 summarizes the documentation that is to be generated for the project types that DelDOT defines. Though not required on the lower-tier project types, all projects should generally include a review of the safety features within the project area.

4.1.3.1 New Construction

This project type consists of all new construction on a new alignment where no road is present for the majority of the project. An example of a new construction project is a bypass constructed to carry through traffic around a population center, construction of a new access route linking an existing highway with a new recreational facility, or a new grade separated facility. New construction projects should be built to achieve full design standards. Design exceptions for this project type should be rare; however, when required, design exceptions must be documented in accordance with the guidance in Section 4.1.4. It is noted that the Council on Transportation (COT) has final approval authority for all corridor route projects in connection with new road alignments in accordance with 29 Del. C. § 8409(b)(4).

4.1.3.2 Reconstruction (4R)

Department Resources
Design Criteria Form

Reconstruction (4R) projects are projects that utilize an existing roadway alignment or make only minor changes to an existing alignment but involve a change in the basic roadway type. Typical work includes improving operation by widening, horizontal and/or vertical realignment, addition of travel lanes, access improvement, and replacing bridges. While reconstruction (4R) projects typically follow an existing road corridor, it may deviate significantly in width and alignment from the present road to achieve full geometric standards requiring the acquisition of additional property rights. Retaining the existing alignment means that existing constraints in the current roadway environment will influence design decisions. These project types should meet all standards established in the Design Criteria Form; however, when required, design exceptions must be documented in accordance with the guidance in Section 4.1.4.

4.1.3.3 Resurfacing, Restoration, and Rehabilitation (3R)

Department Resources
Design Control Checklist
Design Criteria Form

This project type consists of resurfacing, restoration, and rehabilitation (3R) of an existing facility with the intention of preserving and extending service life and enhancing highway safety. Resurfacing, restoration, and rehabilitation (3R) projects include placement of additional surface material and/or other work necessary to return an existing roadway, including shoulders, bridges, the roadside, and appurtenances to a condition of structural or functional adequacy. This project type could include pavement improvements of the existing road, minor roadway widening, and typically includes minor drainage improvements within the scope of the project. Resurfacing, restoration, and rehabilitation (3R) projects should make isolated cost-effective improvements to the existing geometrics such as, flattening curves or improving sight distance, roadside shoulder improvements, and construction of select low-cost safety improvements at the site or system-wide level. Resurfacing, restoration, and rehabilitation (3R) projects are typically constructed within existing right-of-way, although some minor acquisitions may be necessary. Resurfacing, restoration, and rehabilitation (3R) projects do not change the basic roadway type by adding through lanes, passing lanes, or auxiliary lanes, although turn lanes and radius improvements at intersections may be involved.

The design team is to complete the Design Control Checklist and Design Criteria Form for these project types. At times, it will be necessary to deviate from the selected design criteria. Projects on the National Highway System (NHS) that do not meet DelDOT’s established design criteria for 3R projects must document a design exception in accordance with Section 4.1.4. Projects that are not on the NHS and which cannot meet DelDOT’s established design criteria for 3R projects are to note the deviation on the project’s Design Criteria Form. In addition, the design team is encouraged to create a memorandum to the project file explaining the justification for the variances in the design standards. The level of documentation can vary depending on the project intent, environmental concerns, and other issues. In most cases, it is not necessary to provide the same level of documentation as provided in a formal design exception request because the project’s scope inherently precludes making large changes to existing facilities.

4.1.3.4 Preventive Maintenance (1R and 2R)

Department Resources
Design Control Checklist

This project type is often associated with maintenance activities and primarily consists of performing resurfacing and restoration of existing infrastructure that preserves the system, retards future deterioration, and maintains or improves the functional condition of the system without increasing structural capacity. Any enhancements within this alternative type are typically minor and are generally intended to restore the overall condition of the transportation facility. Functionally, Federal-aid eligible preventive maintenance activities are those that address aging, oxidation, surface deterioration, and normal wear and tear from day-to-day performance, and environmental conditions. Preventive maintenance activities extend the service life of the roadway asset or facility in a cost-effective manner. These include roadway activities such as joint repair, seal coats, pavement patching, thin overlays, shoulder repair, restoration of drainage systems, and bridge activities such as crack sealing, joint repair, seismic retrofit, scour countermeasures, and painting.

Preventive maintenance (1R and 2R) projects are encouraged to identify and address isolated or obvious safety deficiencies. In no way shall preventive maintenance (1R and 2R) type projects adversely impact the safety of the traveled way or its users. Preventive maintenance (1R and 2R) projects are encouraged but not required to complete a Design Control Checklist.

4.1.3.5 Miscellaneous Improvement Projects

Department Resources
Design Control Checklist

Miscellaneous Improvement projects are those that do not fit into the other project types and are typically performed beyond the existing edge of pavement. They may also include improvements within the roadway intended to improve safety which do not degrade the existing highway geometrics. These projects are encouraged but not required to complete a Design Control Checklist.

4.1.4 Design Exceptions

Department Resources
Design Control Checklist
Design Criteria Form
Design Exception Request Form
Plan Submission Checklist

The need for exceptions should not be viewed as normal or routine, however, there are occasions where deviation from the selected minimum design criteria established in the Design Criteria Form will be necessary. Deviations from the minimum design criteria for New Construction, 4R, and 3R type projects may require the processing of formal design exceptions in accordance with 23 CFR 625.3(f). The need for exceptions to design criteria are to be identified early in the design process so that approvals or denials will not delay the completion of the design or require extensive redesign of the project. DelDOT’s Plan Submission Checklist requires that design exceptions be processed at the Preliminary Plans milestone submittal; however, the need to evaluate a lower design value may arise at any time during the design process and needs to be addressed expeditiously.

On May 5th, 2016, the FHWA issued a Final Rule (81 FR 27187) which identified the controlling criteria in which deviation requires the processing of a formal design exception as well as established the agency’s expectations for associated documentation. The final rule established two sets of controlling criteria based on whether the roadway is a high-speed or low-speed roadway as shown in Table 4.1.4a and Table 4.1.4b.

Table 4.1.4a – Controlling Criteria on High-Speed Roadways

High-Speed Roadways (i.e., Interstate Highways, other Freeways, and roadways with Design Speed ≥ 50 mph)
Design Speed	Stopping Sight Distance (SSD)
Lane Width	Maximum Grade
Shoulder Width	Cross Slope
Horizontal Curve Radius	Vertical Clearance
Superelevation Rate	Design Loading Structural Capacity

Table 4.1.4b – Controlling Criteria on Low-Speed Roadways

Low-Speed Roadways (i.e., non-Freeways with Design Speed < 50 mph)
Design Loading Structural Capacity	Design Speed

All proposed design exceptions should be thoroughly analyzed, and the potential impacts understood before documentation is submitted for approval. The process to evaluate and justify design exceptions must be based on an evaluation of the context of the facility, needs of all the various project users, safety, mobility (i.e., traffic performance), human and environmental impacts, project costs, and other impacts. Design exceptions are to sufficiently describe all the following:

• Specific design criteria that will not be met,
• Existing roadway characteristics,
• Alternatives considered,
• Comparison of the safety and operational performance of the roadway and other impacts such as right-of-way, community, environmental, cost, and usability by all modes of transportation,
• Proposed mitigation measures, and
• Compatibility with adjacent sections of roadway.

Design exceptions for design speed should be extremely rare as this element establishes most of the other design criteria to be met. Design criteria that cannot be met within a selected design speed should be supported by first seeking a design exception for non-design speed design criteria. When it is determined that a design exception for design speed is required, the documentation should include the length of section with reduced design speed compared to overall length of project and discuss the measures used in transitions to adjacent sections with higher or lower design or operating speeds.

Design exceptions for design loading structural capacity should also be rare. When it is determined that a design exception for design loading structural capacity is required, the documentation should include verification of safe load-carrying capacity (load rating) for all unrestricted legal loads or routine permit loads and, in the case of bridges and tunnels on the interstate, all federal legal loads.

Design exception documentation must include a completed DelDOT Design Control Checklist, DelDOT Design Criteria Form, DelDOT Design Exception Request Form, and all other necessary justification to document the design decision and the proposed mitigation making the selected alternative the best practical alternative.

Design exceptions will fall into only one of the following three scenarios depending on whether the project is an FHWA Project of Division Involvement (PODI) project and its relation to the National Highway System (NHS). The approval process for those three scenarios is described below:

• Design Exceptions on PODI Projects – Variances from design criteria that require design exceptions in this scenario are subject to the approval of the FHWA in accordance with the project’s specific PODI plan. The design exception documentation should be signed by all DelDOT parties before being sent to the FHWA for approval when required. The design team should coordinate the design exception and its recommendation and associated justification with the FHWA before formal approval is sought. Project Managers should refer to the most current Stewardship and Oversight Agreement between FHWA and DelDOT for an up-to-date listing of PODI projects subject to FHWA oversight.
• Design Exceptions on Non-PODI Projects on NHS Routes – Review and approval of variances from design criteria that require design exceptions in this scenario, regardless of funding source, have been delegated to DelDOT through the FHWA and DelDOT Stewardship and Oversight agreement. The final approval authority is the DelDOT Chief Engineer.
• Design Exceptions on Non-NHS Routes – A formal design exception is not required for routes not on the NHS. However, it is DelDOT practice to document variances from design criteria that require design exceptions in accordance with the guidance in this section. The final approval authority is the DelDOT Chief Engineer.

4.2 Road Design

Department Resources
Road Design Manual

Road design is the practice of analyzing and selecting the geometric and physical features that will define a roadway. Many road design elements are dictated by the design standards established in Section 4.1 [NEEDS LINK]; accordingly, design standards should be selected before commencing a project’s road design. DelDOT’s Road Design Manual contains the State specific road design policies and criteria adopted by DelDOT while AASHTO’s A Policy on Geometric Design of Highways and Streets, commonly known as the “Green Book”, and A Policy on Design Standards – Interstate System serve as the primary national road design references. Road design requires careful consideration of a project’s physical, environmental, and related social and economic effects to the surrounding area. Design decisions must reflect the scale of the project and the magnitude of the transportation deficiency being addressed. Strategies for developing a balanced design that properly addresses the system’s transportation needs are presented in Section 3.6 [NEEDS LINK]. The following subsections provide additional road design considerations and presents design guidance developed by DelDOT.

4.2.1 Intersecting Roadways

A location where two or more roadways cross or join is called an intersection. Intersections inherently create conflicting movements that must be managed to ensure efficient and safe operation for all modes of transportation. Traffic control measures that require some or all users to slow or stop instituted to manage these conflict points will affect operation by generally reducing capacity, thereby making these facilities critical in overall transportation network operation. Adding to their complexity, intersections are typically a focus of land use activity.

Traffic counts to obtain turning movement data may be required when analysis of the intersection’s current and/or proposed performance is desired. Information on traffic count requests is contained in Section 3.7.8 [NEEDS LINK].

There are three general types of intersecting roadway configurations:

• At-grade intersections,
• Grade separations without ramps, and
• Interchanges.

4.2.1.1 At-Grade Intersections

Department Resources
Road Design Manual
DE MUTCD
DGM 1-26: Roundabouts
Roundabout Design Criteria Form

At-grade intersections are the most common intersecting roadway type. At-grade intersections range from simple intersections along low volume roadways to complex roadways with high traffic volumes which introduce auxiliary lanes, channelization devices, and various traffic control devices. Common traffic control options available for at-grade intersections include two-way stop controlled, roundabouts, signalized, and all-way stop controlled. The design principles for at-grade intersections are as follows:

• Reduce vehicle speeds through the intersection, as appropriate;
• Provide the required number of lanes and lane assignment to achieve adequate capacity, lane volume, and lane continuity;
• Provide channelization that operates smoothly, is intuitive to drivers, and results in vehicles naturally using the intended lanes;
• Provide adequate accommodation for the design vehicles;
• Meet the needs of pedestrians and bicyclists; and
• Provide appropriate sight distance and visibility.

A warrant analysis should take place when new traffic control options are being considered. The Delaware Manual on Uniform Traffic Control Devices (DE MUTCD) contains the warrant analysis procedures and criteria for at-grade intersections. The DelDOT Road Design Manual summarizes DelDOT’s geometric and design criteria adopted for at-grade intersection. DelDOT Design Guidance Memorandum 1-26 entitled Roundabouts summarizes DelDOT’s guidance for the consideration, planning, design, and construction of roundabouts. DelDOT’s Roundabout Design Criteria Form summarizes the pertinent roundabout design criteria on DelDOT projects. Procedures for analyzing intersection capacity are discussed in more detail in Section 4.4.1.

4.2.1.2 Grade Separations without Ramps

Various types of structures or configurations can be used to grade separate intersecting roadways. The impact to through traffic is minimal when no ramps are provided to connect the intersecting roadways. Configurations can generally be classified as either an overpass or an underpass. Additional information on the geometric design of overpasses and underpasses is provided in the AASHTO Green Book.

4.2.1.3 Interchanges

Department Resources
Road Design Manual

An interchange is a system of interconnecting roadways placed on different grade levels with connecting ramps provided to allow movement between the roadways. Grade separated interchanges offer improved efficiency, safety, and capacity compared to at-grade intersections; however, interchanges are more costly compared to at-grade alternatives. AASHTO establishes warrants for installing interchanges within its Green Book. The DelDOT Road Design Manual summarizes DelDOT’s geometric and design criteria adopted for interchange applications.

4.2.2 Pavement Design

DelDOT’s Materials and Research section is responsible for designing pavement structures that accommodate future predicted traffic needs in a safe, durable, and cost-effective manner in accordance with 23 CFR 626 for all DelDOT contracts and all Department issued agreements and permits. Roadway pavements can consist of either a flexible or rigid pavement structure. Flexible pavement structures rely upon aggregate interlock, particle friction, and cohesion stability to absorb traffic loads. Rigid pavement structures are comprised of a Portland cement concrete slab with a relatively high bending resistance that distributes loads to the base material (if applicable) and then to the subgrade.

The Materials and Research section will work in tandem with the design team to determine the most appropriate pavement type and pavement structure for an individual application. Characteristics that will be analyzed prior to recommending a flexible or rigid pavement structure include, but are not limited to, the following considerations:

• The mixture of traffic on the road,
• The longevity desired before maintenance is required,
• Historical information,
• The functional classification of the road, and
• The constructability of the pavement structure.

4.2.2.1 Pavement Design Request and Recommendation

Department Resources
Standard Construction Details

A request to the Materials and Research section for a pavement design should be submitted by emailing a design request to DOT_Pavementcores@delaware.gov once the scope of the project is known. The pavement design request is often submitted at the same time as the pavement coring request which is discussed in more detail in Section 3.7.7 [NEEDS LINK]. Additionally, the design team can request an adjustment to the thickness of each individual pavement lift during the project development process when determined necessary to match other project characteristics (i.e. tie-ins, milling, etc.); however, in these adjustment cases, the lift thicknesses of the entire pavement section will need to be re-analyzed to ensure that the pavement structure is sufficient. When requesting a pavement structure, it is important to provide the necessary information to the Materials and Research section to perform the design. This information includes the following:

• Proposed milling depth of surrounding pavement,
• Proposed tie-in areas,
• Development in the area that may increase traffic volumes, and
• Purpose of the request (new construction, reconstruction, rehabilitation, redesign).

The Materials and Research section will review the request and provide a pavement design recommendation to the design team. If a flexible pavement structure is recommended, the Materials and Research section will specify which asphalt binder grade and type of stone should be used for each material lift as well as an associated lift thickness. If a rigid pavement structure is recommended, the Materials and Research section will provide the thickness of concrete required and a base course thickness. Reinforcement and joint layout are dictated by DelDOT’s Standard Construction Details. Additional considerations for flexible and rigid pavement structures are provided in Section 4.2.2.2.2 and Section 4.2.2.2.3, respectively.

4.2.2.2 Design Considerations

DelDOT currently performs pavement design in accordance with the methodologies included in AASHTO’s 1993 Guide for Design of Pavement Structures. Therefore, the recommended pavement structure will be based upon the design characteristics of the roadway including:

• Average daily traffic,
• Percent trucks,
• Weight classification of trucks,
• Number of lanes in each direction,
• Directional distribution of traffic,
• Traffic growth rate,
• Functional classification of the road, and
• Historical information.

The recommended pavement structure will utilize a combination of subbase, base course, and surface course materials placed on a subgrade to support the traffic load and distribute it to the roadbed. Figure 4.1.2 contains a pavement cross section displaying the components of a typical pavement structure. The depth of each component of the recommended pavement structure will vary based upon the type of material utilized and the traffic characteristics of the roadway.

Figure 4.1.2: Typical Pavement Cross Section

4.2.2.2.1 Exploration of Existing Subgrade

An important design parameter that must be accounted for in pavement design is the existing subgrade characteristics. Borings may not need to be performed for the design of new low volume roads but may be beneficial on large scale new construction to determine the suitability of underlying soils and if an undercut is required. When resilient modulus information is not available to complete the pavement design, the subgrade is assumed to be in poor condition, and a low resilient modulus is used in the analysis. Soil borings may also aid in determining the cause of failure from the underlying subgrade.

4.2.2.2.2 Bituminous Concrete

Bituminous concrete is a mixture of asphalt binder and well graded high-quality aggregate thoroughly compacted into a uniform, dense mass. Bituminous concrete is considered a flexible pavement structure. The pavement design is based on the structural requirements of the roadway and is composed of different lifts of material. The structural requirements of the roadway are captured in a pavement’s Structural Number. The materials which comprise the pavement structure as well as their associated lift thickness may change provided that the overall Structural Number of the pavement structure remains the same. Table 4.1.2.2-1 contains the structural layer coefficients for the typical materials that DelDOT utilizes in flexible pavement designs. The traffic characteristics of the roadway determine the amount of loading that the pavement structure will be required to resist during its service life.

Table 4.1.2.2-1: Pavement Material Information

Material Type	Binder Grade	Structural Layer Coefficient	Lift Thickness Parameters (inches)
			Minimum	Maximum
Bituminous Type C (4.75 mm mix)	All	0.40	0.50	1.00
Bituminous Type C (9.5 mm mix)	All	0.40	1.25	2.00
Bituminous Type C (12.5 mm mix)	All	0.40	1.50	2.00
Bituminous Type B (19.0 mm mix)	76-22, 70-22	0.40	2.25	4.00
Bituminous Type B (19.0 mm mix)	64-22	0.40	2.25	6.00
Bituminous Type BCBC (25.0 mm mix)	64-22	0.32	3.00	6.00
Graded Aggregate Base Course	NA	0.14	4.00	8.00
Soil Cement Base Course	NA	0.20	4.00	6.00

Standard Type C is 9.5 mm mix. Thin lift applications are to use a 4.75 mm mix. 12.5 mm mix is used only in special circumstances.

The stone that comprises the pavement structure can either be carbonate stone or non-carbonate stone. The choice is based on traffic volumes and speed. Carbonate stone is used when the design ADT is less than 8,000 vpd (vehicles per day) or the posted speed is less than 35 mph. Non-carbonate stone is used when the design ADT is equal to or greater than 8,000 vpd and the posted speed is greater than 35 mph.

Strength in an asphalt pavement comes from the interlock of the aggregates in the mixture. The asphalt binder is used as “glue” that holds the aggregates together to provide stability to the mixture and to prevent water from penetrating the layer. The asphalt binder utilized in a flexible pavement structure is selected based on the type of traffic using the road, the speed of that traffic, the frequency of stops and starts and is referred to using the Superpave Performance Grade (PG) grading system. The PG system is based on the temperature range the asphalt is expected to perform under. The PG rating for an application is selected in accordance with the criteria contained in AASHTO M323 Standard Specification for Superpave Volumetric Mix Design. Binder grade selection on DelDOT projects is summarized in Table 4.2.2.2.2-2. There are additional considerations on PG selection outside of those listed in Table 4.2.2.2.2-2 including whether the existing pavement shows signs of rutting or shoving. Binder grade selection will ultimately be decided by DelDOT’s Materials and Research section.

Table 4.2.2.2.2-2: Binder Grade Selection

Binder Grade Selections
Binder Grade	Traffic Characteristics	Traffic Flow
PG 64-22	Low to moderate trucks and buses	Continuous (no stopping, starting, slowing)
PG 70-22	High truck / bus volume	Continuous
PG 76-22	High truck / bus volume, heavy vehicles	Stopping / standing, slow moving

Performance Grades of the Type C lift and the first underlying Type B lift are to be the same. Subsequent Type B lifts may use a 64-22 binder grade. In situations where the mainline pavement is being overlayed and the road is being widened, the binder grades may not always match the top layer.

4.2.2.2.3 Portland Cement Concrete

Portland cement concrete is considered a rigid pavement structure application. It is critical to consider the joint layout during the design phase. Transverse joints are needed in a rigid slab to act as “controlled cracks” at desired locations and are sealed to prevent water intrusion into the underlying layers. Joints can be keyed, butted or tied. Transverse joints are sawed or formed to a depth of one quarter to one third of the slab thickness. Timing the saw cutting operation to the curing of the Portland cement concrete is critical.

Load transfer devices are used between slabs and usually consist of smooth round dowels. The dowels should distribute the load stresses without over stressing the Portland cement concrete surrounding it, offer little restraint to longitudinal movement of the joint, be mechanically stable under the loads and load frequencies expected during the design period, and be resistant to corrosion from moisture and road salts.

The Materials and Research section will work closely with the design team to prescribe contract requirements and other techniques to mitigate the effect that a Portland cement concrete pavement’s curing time may have on a project’s construction sequencing. There are many additives, including accelerators, that can be added to Portland cement concrete to accelerate strength development and allow the road to be opened in less time than traditionally expected. Precast pavement is also an option in critical areas where closures must be kept to an absolute minimum.

4.2.2.2.4 Pavement Design for Roadway Reconfiguration

Most projects performed by DelDOT include reconfiguration of the existing roadway. If a portion of the roadway is going to be repurposed (shoulders used as through lanes or turn lanes) then a request for cores needs to be submitted with the request for the pavement section. Additional information on requesting pavement cores is provided in Section 3.7.7 [NEEDS LINK]. The Materials and Research section will work with the design team to see if any existing pavement is salvageable or able to be used in the new configuration.

Information used to assess the adequacy of the existing pavement includes:

• Evaluating the need to shift traffic onto non-designated travel lanes (i.e. shoulders, etc.),
• Condition of the existing roadway’s subbase, base course, and surface course materials,
• Feasibility of reuse of the pavement structure,
• Safety of the road surface (skid resistance),
• Rideability of the road surface, and
• Existing striping layout.

4.2.2.2.5 Pavement Design for Rehabilitation

Existing pavements can be rehabilitated as part of a project’s scope. Pavement rehabilitation is most beneficial when the design team determines that the existing roadway materials still have some structural value but will require more intrusive treatment than a typical mill and overlay operation to extend the life of the pavement. A project that falls under this classification should be discussed with the Materials and Research section and be investigated using pavement cores, historical information, and pavement management information to determine the most appropriate rehabilitation method.

There are many existing methods and there are always new methods of rehabilitation in development that can be considered during the design phase of a project. The design team and the Materials and Research section will work together to determine what methodology is most suitable for a project.

4.2.2.2.6 Pavement Drainage

Department Resources
Road Design Manual

Excess water within the pavement and subgrade can lead to premature distress within the pavement structure. Water can enter the pavement structure in a variety of ways, such as through cracks, joints, pavement infiltration, or through groundwater sources. Effects of water trapped within the pavement structure can include:

• Reduced strength of unbound granular materials,
• Reduced strength of roadbed soils
• Pumping of concrete pavements with subsequent faulting, cracking, and general shoulder deterioration,
• Pumping of fines in aggregate base under flexible pavements with resulting loss of support,
• Stripping of asphaltic concrete,
• Differential heaving over swelling soils, and
• Frost heave.

Accordingly, providing adequate drainage of water from pavements is an important design consideration which is justly included in the pavement design methodology utilized by DelDOT’s Materials and Research section. The design team should strive to provide adequate pavement drainage to maximize the pavement structure’s serviceability and the economy of the project’s pavement design. Additional information on pavement structure and subgrade drainage is included in the DelDOT Road Design Manual.

4.2.2.3 Pavement Life-Cycle Cost Analysis

The performance of a pavement life-cycle cost analysis (LCCA) can be beneficial or even required on large scale projects. A pavement LCCA is an economic evaluation technique that considers initial and future agency, road user, and other relevant costs over a defined period to provide a comparative cost between pavement alternatives.

4.2.3 Traffic Calming

Department Resources
Traffic Calming Design Manual

DelDOT defines traffic calming as changes in street alignment, installation of barriers, and other physical measures to reduce traffic speeds and/or cut‐through volumes, in the interest of street safety, livability, and other public purposes. Application of traffic calming techniques is appropriate on subdivision streets and local roads that are intended to primarily serve the purpose of providing access to properties. When applied properly, traffic calming is a key tenet of DelDOT’s complete streets mission as it reduces vehicle volume and/or speed which thereby improves quality of life in residential areas and increases pedestrian and bicyclist comfort and safety. The DelDOT Traffic Calming Design Manual establishes DelDOT’s administrative procedures for evaluating the need for and implementing traffic calming measures, offers guidance on applications for traffic calming, and provides guidance on the geometric design, signing, and pavement markings related to traffic calming measures.

4.2.4 Delaware Byways

Department Resources
Delaware Byways Program Guide
Byways website
Context Sensitive Solutions for Delaware Byways Manual

The Byways Program was established by Delaware’s General Assembly in recognition of the scenic, historic, recreational, cultural, and archaeological value inherent within portions of Delaware’s highway system. The program is established in 17 Del. C. § 191 of the Delaware Code. Once a roadway becomes listed as a byway, a corridor plan is created and the roadway is afforded additional considerations and protections to preserve its features. DelDOT maintains a Delaware Byways Program Guide and a Delaware Byways website which summarizes the Byways Program. Additionally, DelDOT has created the Context Sensitive Solutions for Delaware Byways Manual which provides guidance for projects within designated byway corridors. The design team is encouraged to engage the byway sponsors continuously throughout project development to ensure the intrinsic values of the byway are preserved within the work of the project.

4.2.5 Access Control

Access control, which is sometimes referred to as access management, is the limiting and regulating of public and private access to highways with the goal of minimizing interference to the through traffic on a roadway. The benefits of controlling access must be balanced with the rights of property owners to access the transportation network. Effectively managing access to a facility is an economical means of increasing mobility, capacity, safety, and reducing travel times. In Delaware, access is controlled primarily through limiting and properly spacing ingress and egress points to the highway from adjacent properties and through the installation of fences on high functional classification roadways. Access is considered based on the intended function of the roadway with higher functional classification roadways permitting less access than that of lower roadways.

New access is reviewed and regulated through DelDOT’s development coordination process described in more detail in Section 5.7 [NEEDS LINK]. Access management should be considered along existing roadways during the project development process with 17 Del. C. § 146 of the Delaware Code providing DelDOT the authority to acquire property rights to consolidate commercial entrances or to create new commercial interconnections to improve safety. It is noted that 23 CFR 624 requires approval from the FHWA to add any points of access to or exit from roadways designated as an Interstate System, which includes ramps. The factors affecting access control management include:

• Proposed LOS and capacity,
• Type and width of median,
• Spacing of median openings, intersections, and interchanges,
• Traffic control devices and signal spacing,
• Turning and auxiliary lanes,
• Street connections, and
• Crash data.

4.2.6 Rumble Strips

Department Resources
DGM 1-18: Longitudinal Center Line and Shoulder Rumble Strips
Standard Construction Details

Rumble strips are raised or depressed longitudinal patterns located adjacent to or within the travel lane or shoulder and are intended to produce an audible and tactile sensation to indicate that the driver needs to take some type of action. Rumble strips placed directly within edge line or centerline pavement markings are commonly referred to as rumble stripes.

Rumble strips and stripes have been shown to provide traffic safety benefits to reduce roadway departure crashes, but they also have the potential to create excess noise when struck. They may also interfere with bicyclists when installed along a narrow shoulder. DelDOT provides design guidance and warrants for rumble strips in DGM 1-18 entitled Longitudinal Center Line and Shoulder Rumble Strips and construction details for DelDOT’s standard applications are included in DelDOT’s Standard Construction Details.

4.2.7 On-Street Parking

Department Resources
Pedestrian Accessibility Standards Manual
Complete Streets Design Guide

For most roadways, stopping or parking should only be permitted in emergency situations; however, depending on existing and proposed surrounding land use and roadway facility type, providing on-street parking may be a prudent use of the public right-of-way. On-street parking generally decreases through-traffic capacity, impedes traffic flow, and increases crash potential. Where on-street parking is provided, it must meet the accessibility requirements contained in DelDOT’s Pedestrian Accessibility Standards Manual. Additional information on considerations associated with on-street parking is provided in the AASHTO Green Book as well as in the DelDOT Complete Streets Design Guide. The design team should also be aware of and review any relevant municipal codes that may dictate parking requirements.

4.3 Bridges and Structures

Department Resources
Bridge Design Manual

It is of the utmost importance that the design team apply consistent design standards for the many different structure types that DelDOT utilizes within its transportation infrastructure network. Adhering to consistent design standards serves to maintain the safety, reliability, and longevity of the transportation system and aids in ensuring that structures will act in a predictable manner. 23 CFR 625.4(b) outlines the national design standards, policies, and specifications acceptable to the FHWA for various structural design elements. In Delaware, the DelDOT Bridge Design Manual provides guidance and assistance in the standard practice of design related to bridges and all other structures on or over a public roadway. Deviations from the standards included in the DelDOT Bridge Design Manual will at a minimum, require processing of a Design Variance and may also require the development and approval of a design exception in accordance with Section 4.1.4 if the deviation involves one of the controlling criteria. DelDOT’s Bridges and Structures section is tasked with maintaining DelDOT’s structural inventory which includes the inspection, evaluation, prioritization, and rehabilitation of the State’s infrastructure as well as the design oversight of all proposed structures. When available, existing inspection reports should be referenced during the project development process to identify deficiencies and establish the scope of work. This section describes the typical structure types maintained by DelDOT and their pertinent controlling design standards and guidance requirements.

4.3.1 Bridges

Department Resources
Bridge Load Rating Manual
Bridge Design Manual

DelDOT defines a bridge as any structure under the public roadway with an opening greater than 20 square feet and a minimum vertical clearance of 4 feet. A bridge’s unique design elements can generally be subdivided into the following categories:

• Structural – Structural design requires the determination of the loads that the bridge will carry and the subsequent design of the elements that will support those loads. Information on calculating a bridge’s required loading is included in DelDOT’s Bridge Load Rating Manual while DelDOT’s structural design practices for substructure and superstructure elements are contained within the DelDOT Bridge Design Manual. Existing bridges undergoing rehabilitation and that are to remain must have their structural adequacy verified as part of the project development process when structural modification will affect the existing load rating.
• Geotechnical – All structures will ultimately transfer their supported load into the ground. The practice of evaluating the suitability of the ground and its ability to support the loading is considered geotechnical design. Additional information about DelDOT’s geotechnical investigation practices and associated design considerations is included within the DelDOT Bridge Design Manual. Section 3.7.10 [NEEDS LINK] outlines the process DelDOT uses to collect soil borings which are instrumental in the geotechnical investigation process. Section 4.14.2 identifies the best practices, testing, and deliverables that should be provided when soil borings are performed.
• Hydraulic – Bridges over a waterway will need to consider the hydraulic properties of its openings to ensure that storm events are conveyed without encroaching on the roadway and upstream properties. Hydraulic design also entails identifying the waterway forces that may cause scour or other damage to the transportation infrastructure and to mitigate those identified risks. DelDOT’s hydraulic design practices are outlined in the DelDOT Bridge Design Manual – Section 104.

The complexity, scale, and scope of work proposed at a location will greatly influence the project development process employed and the design elements that will be considered. Additionally, the presence of other similar planned projects near a project’s location could also affect the project development process as well. In general, bridge work can either be advertised as an individual contract, included as part of a project bundle, or included in an existing or proposed Indefinite Delivery / Indefinite Quantity (IDIQ) structure maintenance contracts. DelDOT’s Bridge Design Manual contains comprehensive guidance for several of the project types defined within the manual which are:

• New construction and reconstruction projects,
• Intermediate projects, and
• Preventative maintenance.

The design team should evaluate proposed bridge work for potential incorporation of Accelerated Bridge Construction (ABC) methods. ABC methods utilize and apply innovative planning, design, material, and/or construction techniques to reduce the number of onsite construction days required and potentially minimize traffic disruption. Additional information on construction sequencing, phasing, and timing is included in Section 4.7 [NEEDS LINK].

4.3.2 Dams

Department Resources
Bridge Design Manual

7 Del. C. Chap. 42 permits the State of Delaware to protect the public interest by regulating various aspects of dams including dam design. The administrative code implementing regulations for dam design are contained in 7 DE Admin. Code § 5103. The DelDOT Bridge Design Manual also contains additional information related to design considerations associated with dams.

4.3.3 Other Structures

DelDOT utilizes numerous other structures within its transportation infrastructure network, including but not limited to walls, sign structures, traffic signal mast arms, drainage structures, and lighting structures. The design team must be aware of the structures prescribed within the project and understand both the design phase and construction phase design requirements and reviews that will be required.

4.3.3.1 Ancillary Structure Foundations

Department Resources
Standard Construction Details
Traffic Design Manual
Bridge Design Manual

All ancillary highway structures require a foundation to transfer their applied loads into the subsurface. Priority should be given to utilizing one of DelDOT’s typical foundation types included within DelDOT’s Standard Construction Details. DelDOT’s Traffic Design Manual includes preferred foundation types for various common ancillary structures dependent on the existing subsurface conditions. DelDOT’s Bridge Design Manual contains guidance for applications which are not included within DelDOT’s Traffic Design Manual. In many cases, these structures will require performance of soil borings as part of the design process. Section 3.7.10 [NEEDS LINK] outlines the process DelDOT uses to collect soil borings which are instrumental in the geotechnical investigation process. Section 4.14.2 identifies the best practices, testing, and deliverables that should be provided when soil borings are performed.

4.3.3.2 Sign Structures

Department Resources
Bridge Design Manual

Large overhead and roadside sign structures will require design to ensure structural integrity. DelDOT’s Bridge Design Manual supplements the AASHTO LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals for these applications.

4.4 Traffic

Department Resources
DE MUTCD
Traffic Design Manual
Traffic Calming Design Manual
Delaware Traffic Lighting Policy
Template Traffic Statement
Delaware Strategic Highway Safety Plan

The project development process requires careful consideration of a project’s effect on the movement of people and goods while also minimizing the level of exposure to potential hazards. These evaluations are primarily performed by and administered through DelDOT’s Traffic Engineering and Traffic Operations sections. The Traffic sections are responsible for overseeing the planning, design, and operation of DelDOT’s roadways by both developing their own projects and by acting as support sections when groups outside of DelDOT Traffic develop transportation projects. DelDOT Traffic maintains resources which globally define several of DelDOT’s practices and procedures related to traffic design:

• The Delaware Manual on Uniform Traffic Control Devices (DE MUTCD) – The FHWA publishes a federal Manual on Uniform Traffic Control Devices (MUTCD) to establish basic uniformity of traffic control devices on all of the nation’s streets and highways. States are required to either adopt the federal MUTCD or develop their own which must be in substantial conformance with the federal version in accordance with 23 CFR 655.603. DelDOT has developed its own DE MUTCD which establishes regulations specific to Delaware.
• Traffic Design Manual – This manual defines the standards and processes that are to be followed in the preparation of design plans for all new or modified traffic system devices owned and/or maintained by DelDOT. The manual also applies to all projects in which DelDOT is serving in an oversight role. It should be noted that this manual does not address the design of signs, pavement markings, or lighting, except when associated with powered traffic system devices.
• Traffic Calming Design Manual – This manual provides the administrative procedures needed to evaluate and implement traffic calming measures, provide guidance on applications for traffic calming, and to provide guidance on geometric design, signing and pavement marking related to traffic calming measures.
• Delaware Traffic Lighting Policy – This policy supports DelDOT’s mission, and outlines the general practices, procedures, and standards that govern roadway lighting designs for state‐maintained roadways in Delaware.
• Delaware Strategic Highway Safety Plan – A comprehensive safety plan that provides a framework for reducing fatalities and serious injuries on all public roads. The plan is required in accordance with 23 CFR 924.9.

DelDOT Traffic’s role as a support section will vary depending on whether the project is being developed by DelDOT staff or by staff under a professional services agreement. DelDOT Traffic will typically provide the deliverables described within this section when projects are developed by in-house DelDOT staff and will act in a review and approval authority role when projects are developed by staff under a professional services agreement. DelDOT Traffic also manages the construction and maintenance of traffic control features like signal mast arms and poles, signage, pavement markings, wiring, signals, cameras, junction wells, and detection through IDIQ (Indefinite Delivery / Indefinite Quantity) contracts.

In addition to the plans and specifications that must be developed for a project, each project requires the development of a traffic statement. A template traffic statement is available for download on DelDOT’s website. The traffic statement includes the following information:

• Traffic involvement level on the project for signals, integrated transportation management system (ITMS), highway lighting, signing, and pavement markings.
• A cost estimate for the traffic contractor and traffic supply items. The cost estimate produced by the traffic statement considers the established IDIQ traffic construction costs.
• The contract plan’s sign schedule.
• Summary of the sole source items to be used on the contract.

DelDOT Traffic will create a traffic handoff package at the time the project moves from the design phase into the construction phase. The handoff package will include the following items (as required):

• Handoff form,
• Work Hour Restrictions Checklist (see Section 4.7.1.7 [NEEDS LINK] for more information),
• Press release,
• Traffic statement,
• Signal and ITMS plan,
• Approved signal timing sheet provided by the Traffic Management Center (TMC),
• Specialized equipment quotes, and
• Support section self-clearance documentation for Traffic-only projects.

4.4.1 Capacity Analysis

Department Resources
Road Design Manual

Capacity analysis is used to evaluate the operational characteristics of a facility in terms of defined performance measures. Capacity is typically described in terms of a level-of-service where traffic operation is graded through a system of letter grades ranging from A through F. Additional information on capacity analysis is included in the DelDOT Road Design Manual. DelDOT’s Traffic section will also use software programs including, but not limited to, Synchro, HCS, and VISSIM to perform traffic capacity analysis of transportation facilities.

4.4.2 Traffic Safety

Department Resources
Policy Implement T-07: Safe System Approach

DelDOT strives to provide users with a safe operating environment consistent with the principles outlined in DelDOT Policy Implement T-07 entitled Safe System Approach. Accordingly, the design team should evaluate the existing crash history and explore opportunities to improve safety as part of the project development process. The process for collecting crash data is included in Section 3.7.5 [NEEDS LINK]. The traffic safety analysis conducted should consider the frequency of crashes, crash severity, and mitigate risk factors. Addressing crashes in this manner is considered a reactive response. DelDOT also addresses crashes proactively through its Highway Safety Improvement Program (HSIP) which is further described in Section 2.2.5.3 [NEEDS LINK].

Crashes are seldom the result of a single cause and are usually the outcome of several influences. For this reason, the DelDOT Safe System Approach adopts a roadway design hierarchy which groups engineering and infrastructure-based countermeasures and strategies relative to their alignment with the Safe System Approach. The hierarchy is a project-based, site assessment tool that should be utilized to identify and prioritize countermeasures and strategies on a project. The tiers in the hierarchy are arranged from most to least aligned with the Safe System Approach. Tiers 1 – 3 of the hierarchy emphasize removing potential roadway conflicts and separating vulnerable road users from traveling vehicles, whereas Tier 4 focuses on countermeasures and strategies intended to alert roadway users to conflicts so that they can take appropriate action. The roadway design hierarchy is structured in recognition that physical changes made to the roadway are more effective than changes that rely on road users to make safe decisions. The tiers of the roadway design hierarchy as well as a brief description of the principles of the tier are provided below:

• Remove Severe Conflicts – This tier involves separating road users moving at different speeds or different directions in space to minimize conflicts with other road users. This tier includes strategies that remove conflicts such as intersection crossing conflicts, removing fixed objects along the roadside, or eliminating railway-highway crossings. Strategies in this tier may also include providing physical separation between motorized and non-motorized users to remove conflicts or providing varying degrees of buffered separation to reduce risk of collisions.
• Reduce Vehicle Speeds – This tier includes utilization of design features and speed management strategies to reduce vehicle speeds, thereby reducing the kinetic energy involved in a crash should it occur. From a design perspective, this tier consists of selecting an appropriate design speed, implementing traffic calming measures, and applying self-enforcing roadways. Self-enforcing roads involve the use of road and roadside design elements, such as lane narrowing, intersection channelization, and horizontal and vertical deflection, to elicit lower travel speeds of motor vehicles along the roadway. This also includes features for pedestrians and bicyclists, such as median islands, raised crosswalks, and buffered bicycle lanes.
• Manage Conflicts in Time – This tier assumes that users will need to occupy the same physical space on the roadway but creates a safer environment by separating the users in time using traffic control devices.
• Increase Attentiveness and Awareness – This tier involves increasing attentiveness and awareness by alerting roadway users to certain types of conflicts so that appropriate action can be taken.

It is difficult to completely separate safety and economic considerations within the project development process as incorporating safety features typically has an economic cost. Safety countermeasures also have varying levels of effectiveness depending on numerous site-specific factors. To assist designers in the complex task of evaluating traffic safety, AASHTO has published the Highway Safety Manual. Among the information contained within the manual are methodologies for estimating safety performance of highways and streets including a predictive method for estimating crashes. The predictive method relies on base condition information as well as published crash modification factors (CMFs) to determine a future crash frequency and severity. Crash modification factors are numerical values applied to compute the expected number of crashes expected after implementing a countermeasure on a roadway or an intersection. The predictive method in combination with crash modification factors enables the determination of an anticipated reduction in societal cost. The reduction in societal cost can be considered the benefit of the improvement which can be compared to the projected cost of the improvement as part of a cost-benefit analysis. The Highway Safety Manual includes crash modification factors (CMFs) and additional crash modification factors are available through a CMF clearinghouse funded through the FHWA. DelDOT’s Traffic Engineering section can be used as a resource during this assessment process.

It is noted that 23 U.S.C. 407 establishes that reports, surveys, schedules, lists, or data compiled or collected for the purpose of identifying, evaluating, or planning the safety enhancement of potential crash sites, hazardous roadway conditions, or railway-highway crossings are protected from being subject to discovery, admitted into evidence in a federal or state court proceeding, or for being considered for other purposes in any action for damages arising from any occurrence at a location mentioned or addressed in such reports, surveys, schedules, lists, or data.

4.4.3 Traffic Signals

Department Resources
DE MUTCD
Traffic Design Manual
DGM 1-27: Electric Power Service Request for Roadway Lighting, Traffic signals and ITS Equipment
Voltage Drop Calculator

The DE MUTCD defines a highway traffic signal as a “power-operated traffic control device which traffic is warned or directed to take some specific action”. The DE MUTCD and the DelDOT Traffic Design Manual provide the pertinent requirements and design procedures for DelDOT traffic signals.

The design team will need to coordinate all proposed traffic signals and upgrades to existing traffic signals with the Traffic Design section during the project development process. All required temporary and permanent traffic signal timing will be performed or reviewed by DelDOT’s Traffic section. All new traffic control signals proposed require a signal warrants analysis in accordance with the DE MUTCD be performed and the processing of a traffic signal resolution. In accordance with 29 Del. C. Chap. 84, the Secretary delegates approval and signature authority to sign traffic control rules, regulations and orders pursuant to 17 Del. C. § 141 and 21 Del. C. § 4505 to the following positions:

• Permanent traffic control orders to Chief of Traffic Engineering,
• Temporary traffic control orders to Chief of Traffic Operations, and
• Traffic control orders for bridges and structures to Chief of Bridges and Structures.

Traffic signals require a powered connection. To avoid delays during construction, a power service location must be identified and coordinated during the project development process. DelDOT maintains specific guidance for performing this coordination on capital projects in DGM 1-27 entitled Electric Power Service Request for Roadway Lighting, Traffic Signals and ITS Equipment. When applicable, voltage drop calculations are to be performed by the design team through use of DelDOT’s Voltage Drop calculator.

4.4.4 Roadway Lighting

Department Resources
Traffic Lighting Policy
DGM 1-27: Electric Power Service Request for Roadway Lighting, Traffic signals and ITS Equipment
Voltage Drop Calculator

The primary purpose of roadway lighting is to provide improved visibility at nighttime, thereby increasing traffic safety and overall user comfort. The benefits of roadway lighting must be balanced with several associated negative effects which include increasing nighttime light pollution, initial construction costs, continuing costs for operation and maintenance, and the introduction of fixed objects into the roadside. Roadway lighting is regulated in 7 Del. C. Chap. 71A. DelDOT additionally maintains a Traffic Lighting Policy which prescribes lighting warrants and pertinent design policy and criteria related to roadway lighting. The policy is only intended to prescribe policy for traffic safety purposes; however, if lighting is used for other purposes like crime prevention, the lighting design must meet the requirements in DelDOT’s lighting policy and another entity must agree to fund the construction and utility costs, as well as the on‐going maintenance of the system.

Roadway lighting systems require a powered connection. To avoid delays during construction, a power service location must be identified and coordinated during the project development process. DelDOT maintains specific guidance for performing this coordination on capital projects in DGM 1-27 entitled Electric Power Service Request for Roadway Lighting, Traffic Signals and ITS Equipment. When applicable, voltage drop calculations are to be performed by the design team through use of DelDOT’s Voltage Drop calculator.

4.4.5 Signs

Department Resources
DE MUTCD
Delaware Standard Highway Signs

Signs are used along roadways to provide regulations, warnings, and guidance information for road users. The DE MUTCD contains the State’s standards for signing applications. The FHWA provides a Standard Highway Signs (SHS) Publication of federally standard signs which is supplemented by a publication produced by DelDOT entitled Delaware Standard Highway Signs.

4.4.6 Pavement Markings

Department Resources
DE MUTCD
Temporary Pavement Markings Policy

Markings on pavement are provided to guide and inform the road user. Additionally, most self-driving systems rely heavily on pavement markings. Markings can be used to supplement other traffic control devices or may be used alone to effectively convey information necessary to the user. Pavement markings have limitations that must be considered during the design process. The visibility of markings can be limited by snow, debris, and water on, or adjacent to, the markings. Additionally, pavement markings will wear over time requiring eventual replacement. The DE MUTCD contains the State’s standards for pavement marking applications. Project limits should be considered during the design phase to plan how the proposed improvements will tie into existing pavement markings.

The most common pavement marking applications in Delaware are pavement striping and snowplowable raised pavement markers. Additionally, delineators, curb markings, colored pavements, channelizing devices, and striped islands are considered pavement marking types as well. Different materials can be used as pavement striping each with varying performance and service life limits. DelDOT has published striping item usage guidelines to document material usage practices. DelDOT’s guidance is based upon specification year as shown in Table 4.4.6. Guidance on placing temporary pavement markings is included in DelDOT’s Temporary Pavement Markings Policy memorandum.

Table 4.4.6 – Striping Item Guidelines by Specification Year

Striping Item Guidelines
2025 Standard Specifications	Striping Item Guidelines
2020 Standard Specifications	Striping Item Guidelines

4.4.7 ITS Devices

Department Resources
Traffic Design Manual
DGM 1-27: Electric Power Service Request for Roadway Lighting, Traffic signals and ITS Equipment
Voltage Drop Calculator

Intelligent Transportation System (ITS) devices are electronics, communications, or information processing systems used singly or in combination to improve the efficiency and safety of a transportation network. DelDOT’s ITS devices are connected to DelDOT’s Integrated Transportation Management System (ITMS) network. When properly utilized, these devices are cost-effective tools for providing safe and efficient movement of people and goods. As with other infrastructure elements, ITS devices can be most efficiently implemented when considered early in the project development process. DelDOT’s Traffic Design Manual contains design criteria and associated design preferences for DelDOT’s most common ITS devices including the following:

• System loops,
• Real-time traffic monitoring stations (RTMS),
• Automatic traffic recorder (ATR) stations,
• Bluetooth monitoring stations,
• CCTV cameras,
• Changeable message boards,
• Non-intrusive vehicle detection,
• Weather stations, and
• Variable speed limit signs.

ITS devices typically draw power from a nearby source. Power requirements for ITS devices vary based on system and should be coordinated with DelDOT Traffic. When an external power source is determined necessary, the power service location must be identified and coordinated during the project development process to avoid delays during construction. DelDOT maintains specific guidance for performing this coordination on capital projects in DGM 1-27 entitled Electric Power Service Request for Roadway Lighting, Traffic Signals and ITS Equipment. When applicable, voltage drop calculations are to be performed by the design team through use of DelDOT’s Voltage Drop calculator.

4.5 Non-Motorized Transportation

Department Resources
Policy Implement O-06: Complete Streets Policy
Complete Streets Design Guide
Bicycle and Pedestrian Count Program Guide

Considering and designing for all modes of transportation is the foundational principle of DelDOT Policy Implement O-06, entitled Complete Streets Policy. The policy establishes DelDOT’s objective of providing a comprehensive, integrated, and connected transportation network that is safe and efficient for all modes of transportation, including both motorized and non-motorized methods.

Non-motorized transportation is an integral and critical part of the local and even regional transportation network. Proper accommodation of non-motorized users helps to reduce motorized traffic congestion, provides environmental benefits, enhances transit service effectiveness, offers public health benefits, increases accessibility for all, promotes safety, and can even spur economic vitality. DelDOT is permitted under 17 Del. C. § 132(h) of the Delaware Code to work in conjunction with any political subdivision of the State and with any private organization to plan and construct bicycle and pedestrian transportation facilities in municipal or other locations where DelDOT may not otherwise have the authority to do so.

Non-motorized transportation modes are generally considered to consist of both pedestrians and cyclists. While pedestrians and cyclists are often thought of together in the design process, they have different characteristics and user needs which are further described in Section 4.5.1 and Section 4.5.2. Strategies for accommodating all users, including bicyclists and pedestrians within the transportation network are established in DelDOT’s Complete Streets Design Guide.

The need to consider all users’ needs and abilities is heightened when considering and designing the non-motorized transportation network. Pedestrian and cyclist counts can be used to provide beneficial quantitative and qualitative information that can be used to inform the design. DelDOT’s Bicycle and Pedestrian Count Program Guide documents DelDOT’s considerations for as well as processes for collecting volume counts on these modes of transportation.

4.5.1 Pedestrians

Department Resources
Pedestrian Accessibility Standards (PAS) Manual
Template RPE Form
Accessibility Videos
ADA Plan Review Checklist
RPE Review Checklist
Standard Construction Details
Interim Guidelines for the Installation of Accessible Pedestrian Signals

Pedestrian facilities provide a key connection point in the multi-modal network with nearly every trip including a pedestrian portion; even trips taken by passenger vehicles or transit begin with drivers and passengers walking from their origin to the vehicle and end with them walking from the vehicle to their destination. In urban areas, pedestrians are more prevalent and their needs are more pronounced; however, they must also be considered in rural areas. 17 Del. C. § 132 (f) of the Delaware Code requires that DelDOT plan and construct sidewalks whenever it widens, constructs, or reconstructs any major arterial, minor arterial, collector road, or proposed road in an urbanized area of the State when there is an existing or reasonably anticipated need for sidewalks.

Pedestrians are the most vulnerable of roadway users; therefore, particular attention should be paid to pedestrian safety during design. A project’s design should strive to separate dedicated pedestrian facilities, maximize pedestrian visibility, provide direct pathways, encourage crossings at locations meeting other transportation network users’ expectations, and discourage crossings at unanticipated locations. As with other elements of design, accommodating for pedestrians may require tradeoffs for other network users which must be carefully balanced by the design team.

Where pedestrian facilities are provided, they must be accessible in accordance with the Americans with Disabilities Act (ADA) of 1990 (42 U.S.C. 12101 et seq.). Accessibility requirements are nuanced and generally dependent on a project’s scope. DelDOT’s adopted accessibility standards for the public right-of-way as well as comprehensive design guidance for pedestrian facilities is included within DelDOT’s Pedestrian Accessibility Standards Manual (PAS Manual). A request for practical exception (RPE) will need to be processed whenever DelDOT’s accessibility standards are unable to be met. DelDOT maintains a template RPE form to standardize documentation and to assist the design team with capturing the necessary level of information. DelDOT also maintains accessibility videos, an ADA Plan Review Checklist, and an RPE Review Checklist. Providing accessible facilities during construction activities is required under the Americans with Disabilities Act. Therefore, the design team must consider a project’s accommodation of pedestrians during the construction phase as well. Additional information on planning and designing pedestrian facilities is included in the AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities. DelDOT’s Standard Construction Details includes several details for pedestrian facilities.

Requests to provide audible pedestrian signals may arise during the public involvement process or during the design phase of a project. These requests are to be provided to and evaluated by DelDOT’s Traffic section in accordance with DelDOT’s Interim Guidelines for the Installation of Accessible Pedestrian Signals.

4.5.2 Cyclists

Department Resources
DGM 1-28: Directional Tactile Surface Indicators (DTSI) for Bicycle Ramps
DE MUTCD

Bicycles, or other similar wheeled devices, can be used for recreation or can be used for transportation from home to work, school, shopping, entertainment, or other similar activities. Cyclists, with varying levels of skill and comfort, should be expected on all streets, roads, and highways except where prohibited by law. Providing cyclists with dedicated facilities reduces conflicts with motor vehicles, which in turn can improve traffic operations and safety.

Like pedestrians, cyclists are also considered vulnerable roadway users. In recognition of their vulnerability, facilities for cyclists should be designed to be as low-stress as possible to create a comfortable experience for the user, regardless of their operating capabilities. There are many different methods for accommodating cyclists in a project’s design with the most appropriate method generally being a function of the intended design user profile, project scope, surrounding land use, and other environmental constraints. The AASHTO Guide for the Development of Bicycle Facilities provides guidance on facility selection as well as presents guidance related to geometric design and use of various traffic control devices. NCHRP Research Report 1043 entitled Guide for Roundabouts presents strategies for accommodating cyclists at roundabouts and DelDOT Design Guidance Memorandum 1-28 entitled Directional Tactile Surface Indicators (DTSI) for Bicycle Ramps offers additional design information related to the use of directional tactile surface indicators at bicycle ramp locations. The DE MUTCD provides traffic control strategies that increases the predictability of both bicycle and motor vehicle movements.

4.6 Transit

Department Resources
Standard Construction Details
DTC Bus Dimensions
PAS Manual
DGM 1-27: Electric Power Service Request for Roadway Lighting, Traffic Signals, and ITS Equipment
DTC-05.01: Bus Stop and Passenger Facilities Policy

Transit facilities play a crucial role in DelDOT’s multimodal transportation network by providing an interconnection point for different modes of travel. Among the benefits of a properly planned and designed transit network are the provision of access to affordable public transit options to users who may not have access to or the ability to drive, safety enhancement, reduction of traffic congestion, and promotion of environmental sustainability. Transit relies on a strong multi-modal system; therefore, providing pedestrian and cyclist facilities in addition to vehicular access is essential to achieving the intended benefits of the transit network.

Public transit operators in Delaware include the Delaware Transit Corporation (DTC) as well as Southeastern Pennsylvania Transportation Authority (SEPTA) and Cecil Transit. DTC is an operating Division of DelDOT. In its role, DTC operates the State’s public transit system which also includes the planning of these services. DTC provides services that include but are not limited to fixed route including intercounty and seasonal bus, paratransit, Microtransit, and commuter train services through SEPTA. Paratransit is designed for customers with disabilities and includes door-to-door service whereas Microtransit is designed to serve all customers within a designated Microtransit service area and provides curb to curb service. The common public use facilities that DTC maintains to provide these services includes park-and-rides, transit centers, and bus stops. In its planning role, DTC performs outreach to the public as well as coordinates with other regional transit operators to obtain and provide feedback, comments, and requests directly to DelDOT’s project design teams.

DTC has a dedicated budget for designing and constructing transit facilities; however, in general, it is more economical to construct minor transit facilities as part of an existing planned DelDOT capital project. Accordingly, DTC will contact a project’s design team to recommend the inclusion of transit related facilities and infrastructure as part of the typical DelDOT project development process. These requests are most commonly for new bus stops but may also include requests for relocating existing bus stops, new or modified bus bays, new or upgraded pedestrian or cyclist facilities, addition of reserved bus lanes, or ITMS systems like transit signal prioritization. All such requests should be evaluated in relation to the project’s scope and with input from the appropriate DelDOT stakeholders. Inclusion of these facilities into a Federal-aid highway program project is permissible in accordance with 23 CFR 810. DTC may also originate large standalone projects for facility construction which are then assigned to appropriate DelDOT project development sections within DelDOT. It is noted that projects which receive funds through the Federal Transit Administration (FTA) may be subject to the federal oversight requirements in Title 49 of the Code of Federal Regulations which are not explicitly covered in this manual.

The primary design reference for transit facilities in Delaware is DTC Policy Implement DTC-05.01 entitled Bus Stop and Passenger Facilities Policy. Information on bus stop layout is included within DelDOT’s Standard Construction Details. Additional information on relevant transit facility design is included in the AASHTO Guide for Geometric Design of Transit Facilities on Highways and Streets, the AASHTO Guide for Park-and-Ride Facilities, and the AASHTO Guide for High-Occupancy Vehicle Facilities. DelDOT and DTC also collectively maintain common DTC Bus Dimensions which can be used as a reference as part of the project’s geometric design.

All transit facilities constructed must meet the requirements of the Americans with Disabilities Act (ADA). DelDOT’s ADA standards for facilities constructed within the public right-of-way are provided in the DelDOT Pedestrian Accessibility Standards (PAS) Manual. The United States Department of Transportation’s ADA requirements for transportation vehicles and passenger vehicles is provided in 49 CFR 38 and 49 CFR 39, respectively.

Transit facilities may require power. DTC prefers to supply power to its facilities through solar panels; however, in shaded areas or other areas where solar panels are not sufficient, a power hookup to the local electric utility may be required. In these instances, the project team should follow the process documented in DelDOT Design Guidance Memorandum 1-27 entitled Electric Power Service Request for Roadway Lighting, Traffic Signals, and ITS Equipment.

4.7 Construction Phasing, Sequencing, and Timing

Department Resources
Work Zone Safety and Mobility - Procedures and Guidelines
DGM 1-21: Use of Temporary Traffic Barrier in Work Zones
Guidelines for the Use of Uniformed Law Enforcement Officers in Work Zones
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy

The construction of a project has the potential to increase the risk of crashes and also commonly interrupts traffic patterns, thereby decreasing network mobility. Accordingly, transportation agencies evaluate a project’s construction-phase impacts and implement work zone management strategies to: ensure the safety of all multimodal users and workers; maintain access to properties within the work area; minimize delays, detours, and closures; and support timely project completion. Managing a work zone can consist of any combination of demand management, corridor/network management, safety management, traffic enforcement, and work zone traffic management. The design practice of selecting work zone management strategies that best balance the needs of the traveling public, workers, and other stakeholders with overall project constructability is referred to by many different names; however, for purposes of this manual, the practice is referred to as construction phasing and sequencing. Construction timing is also included in this section as it is directly correlated to the work zone management strategies that are implemented. This section outlines the design considerations that go into developing a project’s construction phasing and sequencing, as well as the deliverables which are to be produced as part of the DelDOT project development process.

Due to the importance of work zone safety and mobility, 23 CFR 630 Subpart J requires states to implement a policy for the systematic consideration and management of work zone impacts on all Federal-aid highway projects. 23 CFR 630 Subpart J further encourages states to apply their work zone safety and mobility policy to all projects regardless of funding source. In addition, 23 CFR 630 Subpart K requires states to develop policies, processes, procedures, or guidance which systematically address the use of positive protection devices to prevent the intrusion of motorized traffic into the work space and other potentially hazardous areas in the work zone; exposure control measures to avoid or minimize worker exposure to motorized traffic and road user exposure to work activities; other traffic control measures including uniformed law enforcement officers to minimize work zone crashes; and the safe entry/exit of work vehicles onto/from the travel lanes. DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines is the policy document DelDOT has developed to meet its obligation under 23 CFR 630 Subpart J and DelDOT’s Design Guidance Memorandum 1-21 entitled Use of Temporary Traffic Barrier in Work Zones and DelDOT’s Guidelines for the Use of Uniformed Law Enforcement Officers in Work Zones are the guidance documents that DelDOT uses to satisfy the requirements of 23 CFR 630 Subpart K. Collectively, these documents establish DelDOT’s practices for managing the safety and mobility aspects of all DelDOT projects and define DelDOT’s use of temporary traffic barrier in work zones, regardless of funding source. These federally mandated resources are further supported by DelDOT Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy. This policy establishes a uniform approach to minimizing traffic impacts resulting from planned lane and road closures and requires a formal coordination effort among DelDOT stakeholders to develop a strategy to complete necessary activities within a safe work zone that is least impactful to the transportation network and the traveling public.

DelDOT’s Traffic Safety section is staffed with construction phasing and sequencing subject matter experts. The section performs a critical role in the management of active work zones as well as in planning, designing, reviewing, and approving aspects of work zones being designed as part of the project development process. The section’s role in the DelDOT project development process varies depending on whether a project is developed through a professional services agreement or by DelDOT staff. For projects developed through a professional services agreement, the section will approve a project’s required detour plans and will review all other construction phasing and sequencing deliverables. For projects developed by DelDOT staff, the Traffic Safety section will develop many of the deliverables described in Section 4.7.2 upon the request of the design team. All project deliverables that are developed by the Traffic Safety section are to be reviewed by the design team for accuracy and consistency with the other elements of the project. Regardless of the Traffic Safety section’s role on a specific project, the section should be utilized as needed as subject matter experts and coordinated with as prescribed within this manual.

4.7.1 Design Considerations

Department Resources
DGM 1-21: Use of Temporary Traffic Barrier in Work Zones
Guidelines for the Use of Uniformed Law Enforcement Officers in Work Zones
DGM 1-24: Road User Cost (RUC) Analysis

DelDOT has an obligation to provide a safe work zone design for both workers and to the traveling public. At the same time, the safety of the work zone must be balanced appropriately with potential impacts to mobility and with project constructability. Many strategies can be employed to minimize traffic impact and increase safety; however, these strategies will have varying effectiveness based on a multitude of project specific factors. The strategies selected may impact a project’s anticipated construction duration. As such, it is crucial to consider construction duration in tandem with the strategies chosen when evaluating a project’s overall effect. A project’s construction must be evaluated both individually and holistically within the transportation network so its impacts can be mitigated to the furthest extent practical through the implementation of the necessary safeguards and provisions in the contract.

Work zone safety is increased by reducing the level of exposure to potential hazards for both users of transportation facilities and highway workers. Accordingly, a critical part of creating a safe work zone is evaluating the need for positive protection devices, traffic officers, and other exposure control measures. 23 CFR 630 Subpart K requires the use of positive protection devices in work zones on Federal-aid highway projects where there is an anticipated high operating speed and no means of escape from motorized traffic intruding into the workspace, unless there is an engineering study which determines otherwise. DGM 1-21 entitled Use of Temporary Traffic Barrier in Work Zones provides additional information on the use of positive protection devices in DelDOT’s work zones whereas DelDOT’s Guidelines for the Use of Uniformed Law Enforcement Officers in Work Zones provides guidance on the use of traffic officers.

Project constructability must also be considered in addition to a project’s impact on traffic and safety implications. Constructability considerations related to work zones include, but are not limited to:

• Access to the work – The contractor must be provided the ability to enter and exit the work zone as well as the appropriate access and operating space needed to complete all required work.
• Staging area – Contractors will require varying space on-site to be able to stage and complete all required work per the contract requirements. On-site staging areas required could include laydown space for construction elements and space to separate material stockpiles. A contractor may obtain additional staging areas in addition to any staging areas specified in the contract through agreements made outside of the contract between DelDOT and the contractor.
• Detours and alternate routes – Roadway closures can reduce construction time but can also create untenable congestion on detour or other alternate routes if not properly planned. Planned closures and detour routes should be considered at both the project level and considered regionally with other planned work in the area to mitigate potential undesirable traffic effects. DGM 1-24 entitled Road User Cost (RUC) Analysis provides a standardized methodology for calculating road user costs that are created by lane or road closures.
• Project overlaps – Traffic impacts can be exacerbated if project work zones are not coordinated. Therefore, concurrent work zones within the region should be proactively identified by the project team and plans made to coordinate activities to reduce overall effects to the public.

Effective coordination and communication are essential elements of a successful construction phasing and sequencing design. Accordingly, construction phasing meetings with key stakeholders are a critical tool that can be used to assess a project’s impact, prescribe measured and effective management strategies, and gain consensus and buy-in. In addition to coordinating with internal DelDOT stakeholders, it may also be beneficial to coordinate with external project stakeholders to develop a project’s construction phasing and sequencing. Coordinating with stakeholders external to DelDOT can provide the project team with a valuable understanding of local preferences and priorities. Section 4.7.1.5 provides additional information and consideration on construction phasing meetings. Additional information on coordinating with external stakeholders is included in Section 5.1 [NEEDS LINK]. All external stakeholder commitments made during the project development process are to be documented by the project team member making the commitment. The project team member making the commitment is to communicate the commitment made to all other pertinent team members including the staff that will administer the project’s construction. Typical external stakeholders that should be considered when developing a project’s construction phasing and sequencing include, but are not limited to:

• Residents and businesses,
• Transit owners and operators,
• Local or county governments,
• Other state agencies,
• Utility owners,
• Emergency services,
• Schools,
• Affected railroad owners and operators,
• Other affected transportation agencies, and
• Community special events/interest groups.

4.7.1.1 Work Zone Management Strategies

Department Resources
DE MUTCD
Work Zone Safety and Mobility - Procedures and Guidelines
Guidelines for the Use of Uniformed Law Enforcement Officers in Work Zones
Summary of Production Rates

Many work zone management strategies can be employed to control traffic during construction. Selecting the appropriate strategies is a function of a multitude of project specific factors. All temporary traffic control devices employed as part of a project’s selected work zone management strategies must meet the requirements of Part 6 of the DE MUTCD which sets forth basic principles and prescribes standards for the design, application, installation, and maintenance of traffic control devices for highway and street construction, maintenance operation, and utility work. DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines contains a comprehensive list of work zone management strategies as well as considerations associated with their use. Several of the more commonly used strategies employed in the State are as follows:

• Dictating work hours within a contract so that work is performed during off-peak hours, thereby reducing impact on the traveling public.
• Controlling lanes by performing closures and providing alternate routes, shifting traffic onto an available and usable surface, or reducing lane widths.
• Implementing strategies such as one-lane, two-way operation; two-way traffic on one side of divided highway (contraflow); and reversible lanes.
• Evaluating work zone speed and/or speed enforcement.
• Performing information campaigns or using smart work zones to inform road users of conditions and allow them to plan alternate routes as needed.
• Selecting alternate contracting techniques to mitigate potential traffic impact.
• Employing various accelerated construction methods to expedite work.
• Using uniformed traffic officers in accordance with DelDOT’s Guidelines for the Use of Uniformed Law Enforcement Officers in Work Zones.
• Including incentives/disincentives which compensates the contractor a certain amount of money for each day identified critical work is completed ahead of schedule and assesses a deduction for each day the contractor overruns the incentive/disincentive time.

All work zone management strategies selected must consider their effect on a project’s construction duration. Construction durations can be calculated based on assumed production rates. There are many ways to estimate production rates including through use of DelDOT’s published Summary of Production Rates. Assumed production rates should be discussed and confirmed with the administering Construction section as rates can be affected by many project specific factors. In general, providing larger areas for contractors to work will reduce contract duration but could also create a more significant impact on the traveling public. For example, providing a full road closure during construction may allow for the work to be completed quicker than if performed through intermittent lane closures; however, allowing only intermittent lane closures would require the work be performed outside of peak travel hours, thus potentially reducing overall user delay.

4.7.1.2 Work Zone Impact Assessment

Department Resources
Work Zone Safety and Mobility - Procedures and Guidelines
DGM 1-24: Road User Cost (RUC) Analysis
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy

A project’s work zone and associated temporary traffic control chosen for implementation are to be assessed in accordance with DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines to determine their effect on traffic. This assessment should occur early in the project development process and continue through project completion. Performance of proactive work zone impact assessments can reduce project delays and ultimately lower project costs. The level of assessment required varies based on the scope of the project as well as other project specific factors. In particular, the level of work zone impact assessment required is determined based on whether the project is determined to be significant in accordance with DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines. The final determination of a project’s significance is the responsibility of DelDOT’s Traffic Safety section. A formal project significance determination by DelDOT’s Traffic Safety section can be requested by the design team at any point in the project development process.

The work zone impact assessment should consider impacts on both highway workers and anticipated road users. In accordance with 23 CFR 630.1004, work zone impacts refer to work zone-induced deviations from the normal range of transportation system safety and mobility. Therefore, these impacts may extend beyond the physical location of the work zone itself, including upstream or downstream of the work zone location, other highway corridors, other modes of transportation, and/or the regional transportation network. The extent of work zone impacts will vary based on factors such as:

• Roadway functional classification and geometrics;
• Area type (urban, suburban, and rural);
• Traffic and travel characteristics (volumes, speeds, vehicle mix and classification, etc.);
• Type of work being performed;
• Type of temporary traffic control;
• Distance between workers and traffic;
• Availability of escape paths for workers;
• Time of day/night;
• Seasonal traffic increases and proximity to holidays; and
• Complexity and duration of the traffic impacts.

Work zones and the temporary traffic control strategies chosen for implementation can be assessed both qualitatively as well as quantitatively. Quantitative assessments are typically calculated in terms of delay, which can then be translated into a cost. DelDOT DGM 1-24 entitled Road User Cost (RUC) Analysis provides a standardized methodology for calculating road user costs that are created by lane or road closures. Road user costs consist of calculating both a delay cost and an operating cost along the affected route(s). Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy states that traffic delays and associated road user costs should be calculated for any planned lane or road closure. The calculated road user costs can then be used to inform the project’s allowable vehicular lane closure hours and roadway closures durations described in Section 4.7.2.1.1 and Section 4.7.2.1.2, respectively. DelDOT’s Traffic Safety section will develop the road user costs for contracts developed by DelDOT staff and will review road user costs developed on projects which are designed through professional service agreements.

4.7.1.3 State-Mandated Work Zone Requirements

The State of Delaware maintains several requirements in relation to work zones which must be evaluated as part of the construction phasing and sequencing design process. Though not mandated through regulation, DelDOT’s standard contract language requires that access to adjacent properties be maintained throughout construction; therefore, access must be considered by the project team during the design phase so that any required coordination and considerations for maintaining access can be included and prescribed into the contract prior to the construction phase.

4.7.1.3.1 Night Work

Department Resources
Policy Implement C-10: Construction Night Work

Construction work can be performed at night when there are generally lower traffic volumes to minimize disruption to traffic; however, night work can also create undesirable effects on surrounding land uses which must be considered. The use of night work is dictated by Bond Bill epilogue language. The Bond Bill epilogue language and DelDOT’s associated policy is summarized in Policy Implement C-10 entitled Construction Night Work. A key requirement of the policy is the distribution of a night work survey to gauge public opinion on the use of night work. It is considered best practice to send a night work survey to residents as part of the project development process unless DelDOT plans to fully prohibit the performance of night work as part of the contract. The appropriate time to send the night work survey within the project development process will vary based on many project specific factors. Sending a letter too early in the process may be detrimental as residents may move, the project related information in the survey is subject to change, and as residents may not remember completing the survey. Sending the survey too late and failing to obtain night work approval may necessitate significant and unexpected late project changes. DelDOT offers residents temporary relocation as part of the night work survey in accordance with the Bond Bill epilogue requirements. Requests for temporary relocations are to be brought to the attention of DelDOT’s Right-of-Way section.

In addition to the night work requirements included in the Bond Bill epilogue language, certain municipalities and counties throughout the State require the processing of a waiver. All necessary waivers should be completed prior to project advertisement. Waivers that require the inclusion of the contractor’s contact information should be submitted with a note that states that the information will be provided once it is known (i.e. after contract award).

All projects should include language on how night work will be considered and/or allowed. When relevant, the contract should dictate when in the construction phasing and sequencing that night work is acceptable and not acceptable.

4.7.1.3.2 Noise

7 DE Admin. Code 1149 (4.2.4) of the Delaware Administrative Code establishes maximum noise levels for construction operations, except in emergency situations, as 85 dBA (decibels A-weighted) at the receiving property for a period of one hour. Acceptable noise levels are further reduced between 10 pm to 7 am to 55 dBA. Additionally, municipalities and counties may have additional and potentially more stringent noise requirements.

4.7.1.3.3 Vibration

Vibration caused by construction activities must be limited in accordance with 7 DE Admin. Code § 1149 (6.6) of the Delaware Administrative Code. The design team should analyze the proposed work and the anticipated method of construction in relation to the class zones defined in 7 DE Admin. Code § 1149 (5) to determine if any further mitigation should be pursued to reduce the vibration on nearby properties. When deemed necessary, DelDOT can monitor the construction phase vibrations under contract special provisions to ensure compliance and monitor existing structure conditions. Additionally, municipalities and counties may have additional and potentially more stringent vibration requirements.

4.7.1.4 Alternative Contracting Techniques

Department Resources
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy

Department Resources
DGM 1-24: Road User Cost (RUC) Analysis

DelDOT typically delivers its projects through a project delivery method called design, bid, build. This method of contracting consists of an owner performing a design, soliciting bids and typically awarding the contract to the lowest bidder. There are alternative contracting techniques that can be considered which can aid in managing a project’s level of impact on the traveling public. Utilizing alternative contracting techniques is especially beneficial on large or complex projects to help mitigate traffic impacts. Alternative contracting techniques available for consideration are described in more detail in Section 6.1 of the Project Development Manual. Several of the more common contracting techniques used to mitigate impacts on traffic include Design-Build, Construction Manager/ General Contractor (CM/GC), and A+B Bidding. It is noted that the time value used for any A+B contracting method employed can be informed by the development of road user costs as described within DGM 1-24 entitled Road User Cost (RUC) Analysis.

4.7.1.5 Construction Phasing Meetings

A project’s selected work zone management strategies affect a broad spectrum of stakeholders. It is imperative to consider a project’s effects on stakeholders during the design phase to mitigate potential construction delays. To this point, DelDOT Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy requires that coordination be conducted during the project development phase so all parties understand the construction phasing and sequencing expectations and that those expectations can be communicated to the Executive Management Team and to the public.

Construction phasing meetings with project stakeholders are an extremely beneficial tool that the design team can use to assess a project’s potential impacts and plan mitigation strategies. These meetings should start as early as practical in the project development process but at a plan development stage sufficient to hold meaningful discussion with the project team. In addition to being called construction phasing meetings, these meetings are sometimes referred to as constructability meetings, work zone phasing meetings, and construction coordination meetings. These meetings and supplemental discussions should continue throughout the duration of the project development process. It is also important that the design team coordinate with any necessary external stakeholders that have the potential to control or otherwise affect work schedules including utilities, adjacent land uses, environmental regulatory agencies, or nearby railroads. These external stakeholders may have time-of-year restrictions, require notification before work starts, or require communication during the design and construction phases to coordinate the work among the DelDOT project as well as other affected entities. The DelDOT staff and sections that should be considered for attendance at these meetings include, but are not limited to:

• The administering Construction section,
• Traffic Safety section,
• The project’s Utility Coordinator and potentially utility companies,
• Erosion and Sediment Permits Engineer,
• Community Relations, and
• Other pertinent stakeholders as determined by the Project Manager.

Members of DelDOT’s Executive Management Team may also be invited to the meeting when determined necessary by the Project Manager.

Typical topics that are discussed at a construction phasing meeting include:

• Project purpose and need for context,
• General construction phasing and sequencing for all aspects of construction including utility relocations,
• Anticipated time-of-year restrictions,
• Work zone management strategies and associated temporary traffic control requirements,
• The need for any targeted public outreach campaigns prior to construction,
• The project’s general constructability,
• Phase and contract duration expectations,
• Work that must be done in advance of the project,
• Contracting techniques,
• Allowable work hours,
• Contract road user costs or other incentives or disincentives to control the work,
• Strategies to maintain access to surrounding land uses,
• Stakeholder commitments made,
• Transportation Management Plan (TMP) requirements (see Section 4.7.2.2),
• Potential conflicts or overlaps with other projects in the area,
• The suitability of any accelerated construction techniques,
• The need and methods for work zone monitoring, and
• Upcoming project milestones and schedule.

4.7.1.6 Pedestrian Accessibility

Department Resources
Temporary Service Interruptions Memorandum
PAS Manual

The Americans with Disabilities Act of 1990 (42 U.S.C. 12101 et seq.) requires that the existing pedestrian network be maintained in an accessible condition throughout construction. However, 28 CFR 35.133 does allow for temporary interruptions in service or access due to maintenance or repairs. DelDOT’s policy for the allowance of temporary interruptions is documented in a Department policy memorandum. Additional information on accessibility standards is included in Section 4.5 as well as in DelDOT’s Pedestrian Accessibility Standards Manual (PAS Manual).

4.7.1.7 Work Hour Restrictions Checklist

Department Resources
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy
Contract Work Hour Restrictions Checklist
Location Work Hour Restrictions Checklist

DelDOT Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy requires the completion of DelDOT’s Work Hour Restrictions Checklist before project advertisement or work order issuance. DelDOT’s Work Hour Restrictions Checklist is intended to document mutual commitments made during the construction phasing and sequencing design. DelDOT maintains two separate Work Hour Restrictions Checklists. DelDOT’s Contract Work Hour Restrictions Checklist are for projects that are advertised as a single advertisement whereas DelDOT’s Location Work Hour Restrictions Checklist is for locations or work orders issued under an open-end construction (IDIQ) contract. The checklist is to be completed by the design team and then circulated to the listed signatories with the most current plans and other documents determined necessary by the Project Manager. The completed road user cost calculations should also be included when the Work Hour Restriction Checklist is sent to the Traffic Safety section.

4.7.2 Project Deliverables

Department Resources
DE MUTCD
Standard Specifications
Standard Construction Details

The construction phasing and sequencing design and associated commitments made during the design process must be documented appropriately within the project deliverables to ensure that they are enforceable during the construction phase. The measures included in the contract for facilitating road users through a work zone is called the maintenance of traffic (MOT) plan in DelDOT and is referred to as the temporary traffic control (TTC) plan in the DE MUTCD. Requirements for a project’s MOT plan are established in the DE MUTCD, DelDOT’s Standard Specifications, and DelDOT’s Standard Construction Details. The scope and detail to be included in the MOT plan is determined by the project characteristics and the traffic safety and control requirements identified during the design process. In general, the contract must be prescriptive enough to communicate and enforce previous project team discussions but not so prescriptive as to overly restrict the contractor’s means and methods.

Important and potentially impactful requirements regarding a project’s construction phasing and

sequencing should be clearly included in the project deliverables to ensure the contractor understands the maintenance of traffic responsibilities associated with the project.

4.7.2.1 Contract Plans

Department Resources
Construction Plan Submission Checklist
Example Plans
DE MUTCD
BR-14-002: Guidance for Sequence of Construction for Bridge Replacement Projects

DelDOT projects commonly develop plan sheets entitled “Construction Phasing, M.O.T., and Erosion Control Plan” to provide detailed information describing the construction phasing and sequencing within the contract documents. The elements that should be included in these plan sheets are established in DelDOT’s Construction Plan Submission Checklist and Example Plans. The intent of these plans is to clearly identify the type and character of the proposed work together with any stakeholder commitments made during the design phase. Work zones that follow a typical application in the DE MUTCD should not repeat the TTC devices in the DE MUTCD in the contract plans. DelDOT maintains additional construction sequencing guidance for bridge replacement projects in Engineering Instruction BR-14-002 entitled Guidance for Sequence of Construction for Bridge Replacement Projects.

4.7.2.1.1 Intermittent Vehicular Lane Closures

Department Resources
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy

Department Resources
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy
Design Resource Center

It is often necessary to intermittently close vehicular lanes during construction operations to provide adequate space for the work. Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy states that allowable lane closure hours should be included in all contracts, including locations on IDIQ contracts, and maintenance operation activities which create lane closures. Information on allowable lane closures are typically displayed in the contract plans as a matrix. DelDOT’s Traffic Safety section will develop the lane closure matrix for contracts developed by DelDOT staff and will review lane closure matrices developed on projects which are being developed through professional service agreements. Suggested lane closure hours are included in Appendix A of Policy Implement C-09. The allowable lane closure hours should consider the duration of the closure, the number of lanes on the roadway, number of lanes affected by the work, the conditions created by the closure, traffic characteristics, constructability of the work within the hours provided, and nearby restrictions from other projects. Contract road user costs are to be included in the contract documents to enforce the allowable work hours. Additional information on including contract road user costs is provided in Section 4.7.2.3.1.

4.7.2.1.2 Vehicular Road Closures

Vehicular road closures may be used to accelerate construction or when intermittent lane closures will not provide adequate time or space to perform the construction. Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy requires that closure durations be included in all contracts, including locations on IDIQ contracts, and maintenance operation activities which create road closures. Unless approved otherwise by DelDOT’s Traffic Safety section, roadway closures will require the development of detour plans. DelDOT’s Traffic Safety section will provide a project’s detour plans for contracts developed by DelDOT staff and will review and approve detour plans on projects which are being developed through professional service agreements. Contract road user costs are to be included to enforce contract durations chosen. Additional information on including road user costs in a contract is provided in Section 4.7.2.3.1. Road closures or detours that are not the last phase of a project will need to be tied to a measurable interim project milestone. DelDOT maintains example detour plans for reference on the Design Resource Center.

4.7.2.1.3 Pedestrian Path and Bicycle Route Closures

Department Resources
Design Resource Center

Sometimes it may be necessary to temporarily relocate pedestrians or bicycle routes for construction activities. In these cases, pedestrian path and bicycle route detour plans are required. DelDOT’s Traffic Safety section will develop detour plans for projects developed by DelDOT staff and will review and approve detour plans on projects which are being developed through professional service agreements. DelDOT maintains example detour plans for reference on the Design Resource Center.

4.7.2.2 Transportation Management Plans (TMPs)

Department Resources
Work Zone Safety and Mobility - Procedures and Guidelines

A Transportation Management Plan (TMP) is defined by 23 CFR 630 Subpart J as strategies to manage the work zone impacts of a project. DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines requires the development of a TMP for all DelDOT projects. The information required in the TMP varies based on project scope and whether the project is determined to be significant in accordance with DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines. TMPs can range from the project’s TTC plans to a document which comprehensively addresses both a project’s transportation operations as well as its public information and outreach components. Additional information on developing a project’s TMP is included in DelDOT’s Work Zone Safety and Mobility - Procedures and Guidelines. 23 CFR 630.1012(c) requires that the project’s Plans, Specification, and Estimate (PS&E) package include the TMP or provide provisions for the contractor to develop a TMP at the most appropriate project phase based on the contracting method selected.

4.7.2.3 Lane or Roadway Closure Contract Enforcement

Department Resources
Policy Implement C-09: Planned Lane Restriction and Road Closure Policy
DGM 1-24: Road User Cost (RUC) Analysis

DelDOT Policy Implement C-09 entitled Planned Lane Restriction and Road Closure Policy and DGM 1-24 entitled Road User Cost (RUC) Analysis both encourage the use of mechanisms to enforce contract time restrictions whenever allowable lane closure hours or roadway closures are prescribed in a contract. Including enforcement mechanisms provides the administering Construction section with the tools necessary to enforce the provisions of the contract.

The primary enforcement mechanism DelDOT uses is contract road user costs which are discussed in Section 4.7.2.3.1. A lesser used enforcement mechanism of incentives/disincentives is described in Section 4.7.2.3.2. Contract liquidated damages are sometimes confused as a type of contract road user cost; however, liquidated damages is an amount that is payable to DelDOT by the contractor if the contractor fails to complete the project within the contract time. In accordance with 23 CFR 635.127, liquidated damages are included within the contract as a means to reimburse DelDOT for a range of project costs that at a minimum, are to cover the estimated average daily construction engineering costs associated with the type of work encountered on the project. Liquidated damages are discussed in more detail in Chapter 6.

All contract enforcement mechanisms are to be closely coordinated with the entire project team and especially the administering Construction section.

4.7.2.3.1 Contract Road User Costs

Department Resources
DGM 1-24: Road User Cost (RUC) Analysis
Road User Cost Example Template
Road User Cost Detour Example Template

Contract road user costs is a mechanism where the contractor is assessed either all or a portion of the road user cost calculated in DGM 1-24 entitled Road User Cost (RUC) Analysis as a penalty for violating the contract time restrictions. Contract road user costs are to be included on all contracts and work orders which contain provisions for lane or roadway closures. Provisions for contract road user costs are added to a DelDOT contract or work order by requesting a template through DelDOT’s Engineering Support section. DelDOT maintains two templates for contract road user costs:

• Road User Cost Example Template – This template is used when a road user cost is to be assessed for an intermittent lane closure closing early or opening late.
• Road User Cost Detour Example Template – This template is used when a road user cost is to be assessed for a roadway closure that exceeds its allowable contract duration.

Once the Road User Cost template has been completed and reviewed and approved by internal DelDOT stakeholders, it should be submitted back to DelDOT’s Engineering Support section for processing.

4.7.2.3.2 Incentive and Disincentives

Department Resources
Incentives/Disincentives Template

Contract incentives/disincentives describes a contract provision which compensates the contractor a certain amount of money for each day identified critical work is completed ahead of schedule and assesses a deduction for each day the contractor overruns the incentive/disincentive time. It is primarily intended for critical projects where traffic inconvenience and delays are to be held to an absolute minimum. Incentives/disincentives can be applied to a specific project milestone, overall project completion, or other elements to improve project delivery. DelDOT primarily uses incentives/disincentives provisions for critical bridge projects. The amount of the incentives/disincentives are based upon estimates of factors such as traffic safety, traffic maintenance, and road user costs. DelDOT maintains an Incentives/Disincentives Template that can be requested through the Engineering Support section. When used, the language and amounts should be closely coordinated with the entire project team, the administering Construction section, and with the Executive Management Team.

4.7.2.4 Timing Statements

Department Resources
PS&E Timing Statement Template
Timing Statement Guide
PS&E to Completion Date Contract Time Calculator
Preconstruction Timing Analysis Requirements

DelDOT timing statements are used to summarize a project’s construction phasing and sequencing and other pertinent work restrictions to arrive at a recommended contract duration. An approved timing statement is required prior to PS&E so that a contract duration can be included in the advertisement. Though required at PS&E, construction timing should be considered throughout the project development process to inform decisions on construction phasing and sequencing. Measured and reasonable construction durations in an advertisement are critical to balancing impacts to the traveling public with the goal of receiving cost competitive bids. In recognition of the importance of accurate durations in a contract, 23 CFR 635.121 requires that state Departments of Transportation (DOTs) maintain written procedures for determination of contract time for Federal-aid Highway Projects; however, DelDOT applies the same process to project’s regardless of funding source.

DelDOT’s PS&E Timing Statement Template as well as Timing Statement Guide are available online. In addition to the Timing Statement Guide, DelDOT also maintains a PS&E to Completion Date Contract Time Calculator that can be used as a tool to help estimate project milestones around the contract advertisement period. Projects that are developed through professional service agreements are to develop a critical path method (CPM) schedule as part of developing the timing statement in accordance with the requirements included in DelDOT’s Preconstruction Timing Analysis Requirements document. Development of a CPM schedule on projects developed by DelDOT staff is considered optional depending upon the size, scope, and complexity of the project. The design team should coordinate with project team members as needed while completing the PS&E Timing Statement Template to ensure an accurate contract duration. Once complete, the signed statement is to be uploaded into DelDOT’s Unifier software.

4.8 Roadway Drainage

Department Resources
Drainage Design Workflow

Roadway drainage design is defined as the practice of designing “systems that collect, convey, and discharge stormwater flowing within and along the highway right-of-way” by the FHWA’s Hydraulic Engineering Circular 22 (HEC-22) Manual. DelDOT is assigned responsibility for roadway and adjacent land drainage by 17 Del. C. Chap. 9 of the Delaware Code. The Delaware Code mandates that DelDOT cause adequate drainage of water along the right-of-way caused by construction, alteration, or changes to the natural contours of the land. This section summarizes the standards and practices that DelDOT utilizes to perform drainage design and serves to highlight roadway drainage design considerations relevant to the project development process. As such, this manual is not intended to establish the design methodologies or practices that are used to perform drainage designs within the State.

Roadway drainage design plays a critical role in maintaining the overall serviceability of the transportation network. Proper drainage removes water on or adjacent to the roadway. This reduces the likelihood of hydroplaning and provides a more suitable traveled way. Additionally, the prevention of standing water on and along the roadway helps extend the pavement structure as designed, throughout its lifetime. In general, roadway drainage systems are categorized into two types that often work in tandem:

• Open systems, which intercept and convey runoff through ditches, swales, or other natural or man-made channels, and
• Closed systems, which use inlets, pipes, and/or manholes to convey water.

Roadway drainage design involves two key components:

• Hydrologic assessment, to evaluate the quantity and timing of runoff for various design rainfall events, and
• Hydraulic design, to ensure the system has sufficient capacity to manage runoff without compromising the integrity of the road or surrounding environment.

DelDOT provides a recommended Drainage Design Workflow that illustrates the general steps required to complete a roadway’s drainage design. This resource also contains links to commonly used reference materials. Like many other elements of design, drainage design is an iterative process that builds upon itself. Therefore, interim quality control checks are encouraged to ensure that the drainage design is performed as efficiently as possible.

While software tools can assist in roadway drainage calculations, all deliverables must meet the documentation requirements outlined in the resources referenced in Section 4.8.2. Reports submitted to DelDOT must provide all necessary information, figures, and calculations for review. Submitted reports may include design software outputs as backup documentation for the standard design summaries.

4.8.1 Design Standards and Criteria

Department Resources
Road Design Manual

As with other elements of design, the benefit of conveying drainage is balanced by economic considerations. This balance is primarily achieved by following established design standards. The drainage design standards and associated design criteria unique to the State of Delaware are established in Section 6.2 of the DelDOT Road Design Manual. The Road Design Manual refers to both the FHWA’s HEC-22 Manual and AASHTO’s Drainage Manual as resources for performing roadway drainage design computations. FHWA provides additional drainage design related publications on its Hydraulics Publications webpage, offering a wealth of resources for further reference.

4.8.2 Design Documentation

Department Resources
Drainage Plan Submission Checklist
Sample Drainage Report

Standardization of drainage design documentation serves to expedite reviews and helps promote accuracy and consistency of practice across the State. Additionally, the creation of consistent and clear documentation ensures sound engineering practice while providing a record of decision-making at the project level. Drainage design documentation is primarily achieved through creation of a drainage report.

DelDOT maintains several resources to aid in the development of thorough and consistent drainage reports, including the DelDOT Drainage Plan Submission Checklist and Sample Drainage Report. DelDOT’s standard project development process requires the submission of a draft drainage report and a final drainage report. This staged delivery allows for the drainage design to be completed in phases commensurate with the overall project development process.

4.8.3 Design Considerations

There are many site-specific considerations that must be evaluated at the project level as part of the drainage design process. In general, a project’s drainage design should aim to preserve natural drainage patterns and existing drainage courses to the maximum extent practical, in consideration of the environmental impacts, construction/phasing costs, condition of existing drainage features, and long-term maintenance ramifications. In addition to designing new elements, the project’s drainage design should also consider its effect to the downstream network. Drainage design must also account for conflicts with other subsurface features along roadways including utilities, guardrail, and underground structure foundations. This section outlines several project development related considerations typically associated with roadway drainage design.

4.8.3.1 Tax Ditches

Department Resources
DelDOT Gateway
DGM 1-23: Tax Ditches
Right-of-Way Engineering Manual

Tax ditches are waterways that are constructed through petition filed in the Superior Court of the county in which all or the major portion of the area involved is located. Tax ditches are found in each county in the State with most located in Kent and Sussex County. Tax ditch construction and maintenance is funded through landowners (also referred to as taxables) that have come together to form a Tax Ditch Organization. A Tax Ditch Organization is considered a governmental subdivision of the State under Delaware Code. Delaware’s Tax Ditch Program is administered by the Department of Natural Resources and Environmental Control (DNREC) and established in 7 Del. C. Chap. 41. The design team should investigate for the presence of tax ditches within the project area during project scoping. Tax ditches are included within DelDOT Gateway under the “Hydrology – Tax Ditches” layer.

All potential impacts to these facilities must be carefully considered and mitigated during the design process. The design team must ensure the project does not negatively impact the function of the tax ditch and must also ensure future access for maintenance purposes. Depending on the level of project impact, the design team may need to perform direct coordination with the DNREC Drainage Program. The Project Manager should also coordinate potential impacts to temporary and permanent property rights with the Team Support section. The Team Support section is then tasked with creating agreements with the affected tax ditch managers. A Court Order Change (COC) may be required by DNREC anytime a special access right-of-way (SAR) is required to support alteration or maintenance of a tax ditch. A COC is a time-consuming process and must be properly accounted for in a project’s schedule accordingly. Further guidance on right-of-way considerations associated with tax ditches is prescribed in DGM 1-23 entitled Tax Ditches and the process for coordinating tax ditch agreements is outlined within the Right-of-Way Engineering Manual.

4.8.3.2 Pipe Materials

Department Resources
DGM 1-20: Revised Pipe Materials

Various pipe materials can be used to convey water. Accordingly, the material proposed for new conveyances must be specified within the drainage report and contract documents. DelDOT selects pipe material based on available cover, desired service lives, economic considerations, and any other factors that may affect the performance of the pipe (e.g., soil pH, type of water exposure, susceptibility to abrasion, fire, etc.). DelDOT’s pipe material selection guidance is provided in DGM 1-20 entitled Revised Pipe Materials. Close attention should be paid to pipe cover in relatively flatter areas of the state to ensure proper pipe cover.

4.8.3.3 Drainage Network Discharge

The discharge of roadway drainage involves both regulatory and practical considerations that must be addressed during the design process. It is essential to coordinate the location of outfalls with both the Water Resources section and the Environmental Stewardship Office to ensure that federal and state compliance requirements are met. Additionally, Section 4.10.1.2 should be referenced for guidelines on minimizing scour and erosion at outfall locations.

4.8.3.4 Safety Grates

Department Resources
DGM 1-15: Personnel Grate for Pipe Inlet
Standard Construction Details

There are multiple pipe end treatments available for use, each with a specific and appropriate application. DelDOT maintains specific guidance for installation of safety grates on pipe ends within DGM 1-15 entitled Personnel Grate for Pipe Inlet. A personnel safety grate is an additional component added to pipe end sections that are intended to prevent people and debris from entering the closed drainage system at inlet locations. These grates are not designed for vehicular loadings and should not be considered a traversable design. However, DelDOT maintains separate safety end structure details within its Standard Construction Details which are designed to accommodate vehicular loading in addition to preventing people and debris from entering the pipe. Additional information on roadside design is included within Section 4.11.

4.9 Stormwater Management

Department Resources
ES2M Wiki

The definition of stormwater management varies based on regulatory agency; however, stormwater management generally consists of both a water quantity control and water quality control component. 7 Del. C. § 4002 of the Delaware Code defines stormwater management strictly in terms of its components of water quantity and water quality control as follows:

• Water quantity control – A system of vegetative, structural, and other measures that controls the volume and rate of stormwater runoff which may be caused by land disturbing activities or activities upon the land.
• Water quality control – A system of vegetative, structural, and other measures that controls adverse effects on water quality that may be caused by land disturbing activities upon the land.

The Clean Water Act (33 U.S.C. 1251 et seq.) authorizes the United States Environmental Protection Agency (US EPA) to implement regulations for controlling stormwater runoff from drainage systems. Section 402 of the Clean Water Act allows the US EPA to delegate their authority to regulate stormwater runoff discharge to the states. The requirements of such state administered programs are contained in 40 CFR 123. Delaware, through the Department of Natural Resources and Environmental Control (DNREC), administers its own stormwater runoff discharge program which DelDOT’s projects are then subject to. DNREC’s implementing regulations are contained in 7 DE. Admin. Code § 5101 and referred to as the Delaware Sediment and Stormwater Regulations (DSSR).

7 DE. Admin. Code § 5101 (9.0) further allows DNREC to delegate provisions of the DSSR to Conservation Districts, counties, municipalities, or state agencies. DelDOT maintains status as a delegated agency under the DSSR and is therefore responsible for ensuring that projects comply with the requirements of the DSSR. DelDOT’s responsibilities include stormwater management and erosion and sediment control plan review and construction inspection for DelDOT projects and periodic maintenance inspection of constructed facilities.

Many sections within DelDOT perform roles in support of DelDOT’s responsibilities as a delegated agency. DelDOT’s Water Resources section is tasked with directly overseeing many of the project development related components associated with DelDOT’s delegated agency status. The Water Resources section will provide plan reviews and approvals, maintains technical resources and guidance, and is staffed with subject matter experts that can be consulted throughout the project development process. Among the resources that the section maintains is the DelDOT ES2M Wiki which provides guidance on a wide range of erosion and sediment control and stormwater management topics.

Stormwater is managed through the use of established best management practices (BMPs). 7 DE. Admin. Code § 5101 defines BMPs as “schedules of activities, prohibition of practices, maintenance procedures, and other management practices or measures to prevent or reduce the discharge of pollutants. BMPs include the following, among other practices and measures: structural and non-structural controls; treatment requirements; operating procedures and practices to control site runoff.” Stormwater management BMPs can require dedicated space within the project area to complete. This additional space may require acquisitions or may necessitate land dedication. Therefore, the need for stormwater management BMPs should be considered early in the project development process as they could increase the overall project area, cost, and duration.

Stormwater quantity management and compliance design will require performance of various hydrology and hydraulic (H&H) computations depending on a project’s scope. There are numerous H&H software suites that can be used to perform these calculations and/or iterations of work. Before performing any required H&H modeling, the design team should review DNREC’s list of approved H&H software to ensure adherence to DNREC’s requirements.

4.9.1 Project Development Process

Department Resources
Stormwater Checklist
ES2M Wiki – Concurrence Meeting Agenda
ES2M Wiki – Maintenance Only Projects

As with other design related tasks within the project development process, stormwater management design and coordination are generally performed in a stepped manner. DelDOT’s stormwater management design process is defined in Figure 4.9.1. A key component of DelDOT’s process is the performance of a concurrence meeting between the design team and the Water Resources section. Concurrence meetings encourage early and detailed conversation on both a project’s scope and path to compliance under the DSSR. DelDOT maintains a concurrence meeting agenda on its ES2M Wiki which should be used to guide these meetings and facilitate discussion. The Water Resources section also maintains a DelDOT Stormwater Checklist that should be completed prior to each milestone submission to ensure all required items have been addressed. DelDOT maintenance only projects follow a slightly different project development process which is defined on the ES2M Wiki.

Figure 4.9.1 – DelDOT Stormwater Management Project Development Process

4.9.2 Project Compliance

There are multiple avenues for a project to achieve compliance with the DSSR. DSSR requirements and subsequent compliance is largely determined by the nature of the land disturbing activity being performed, the total area that will be disturbed during the course of the project, and the degree to which the project results in net changes to existing land use. These three factors collectively influence the scope and type of BMPs that must be implemented. To assess and ensure compliance, projects may need to evaluate their stormwater impact under three defined design storm events:

• Resource Protection Event Volume (RPv): The post post-development annualized volume of runoff produced by the storm having a ninety-nine percent (99%) probability of occurrence, or the 1-year, 24-hour rainfall event. It is equal to the runoff volume generated by a 2.7 inch storm event.
• Conveyance Event Volume (Cv): the volume of runoff produced by the post-development storm having a ten percent (10%) annual probability of occurrence, or the 10-year, 24-hour rainfall event.
• Flooding Event Volume (Fv): the volume of runoff produced by the post-development storm having a one percent (1%) probability of occurrence, or the 100-year, 24-hour rainfall event.

The subsections that follow will provide detailed guidance on determining project thresholds, selecting appropriate stormwater control measures, and documenting compliance with DSSR requirements.

As further described in Section 4.9.2 [NEEDS LINK], project compliance can be achieved either by being under 5,000 SF of disturbance, meeting the requirements of a standard plan, or by documenting project compliance in a detailed plan.

4.9.2.1 Projects Under 5,000 SF of Disturbance

Certain land disturbing activities are specifically exempt from the requirements of the DSSR. A listing of activities that are exempt are included in 7 DE. Admin. Code § 5101 (1.4). The exemption most relevant to DelDOT projects is the exemption of total land disturbing activities of less than 5,000 square feet.

4.9.2.2 Standard Plan

A "Standard Plan" is defined by 7 Del. C. § 4002 as “a set of pre-defined standards or specifications for minor land disturbing activities that may preclude the need for the preparation of a detailed plan under specific conditions”. Project types for which Standard Plan Applicability is defined are included within 7 DE. Admin. Code § 5101 (3.7). The four project types most applicable to DelDOT activities as well as their application for Standard Plan approval are included in Table 4.9.2.2.

Table 4.9.2.2 – Typical Standard Plans for DelDOT

Project Type	Application for Standard Plan Approval
Minor Bridge and Culvert Construction	Minor Bridge and Culvert Construction Application for Standard Plan Approval
Sidewalk, Trail, or Other Linear Impervious Surfaces	Sidewalk, Trail, or Other Linear Impervious Surfaces Application for Standard Plan Approval
BMP Construction and Retrofit	BMP Construction and Retrofit Application for Standard Plan Approval
Demolition	Demolition Application for Standard Plan Approval

The Sidewalk, Trail, or Other Linear Impervious Surface Standard Plan type requires documentation that the curve number (CN) change between pre and post construction is less than 1. For these cases, DelDOT maintains a Standard Plan CN Worksheet that is to be used for documentation.

DelDOT projects that meet the requirements of a Standard Plan do not require the construction of a stormwater quality facility (stormwater management BMP); however, water quantity control must still be calculated and shown not to have an adverse impact. The design team should submit the following information to the Water Resources section for Standard Plan Approval:

• Completed application for Standard Plan approval for the applicable project type,
• The project’s drainage report,
• The project’s current and full construction plan set, and
• All applicable documentation to prove Standard Plan compliance including the Standard Plan CN Worksheet and supporting land cover and drainage area documentation.

4.9.2.3 Detailed Plan

Department Resources
ES2M Wiki – Project Level DURMM
ES2M Wiki – Cv & Fv Compliance Flowchart
ES2M Wiki – Stormwater Management Report Format

Detailed Plans are required for projects which are not exempt from the DSSR and which do not meet the applicability requirements of Standard Plans. A key tool required to document a project’s compliance with the DSSR for detailed plans is the Delaware Urban Runoff Management Model (DURMM) which is available on DNREC’s website. DURMM is an excel spreadsheet model that is used to assess stormwater management needs and determine runoff reduction shortfalls or credits. Detailed Plans require the development of a stormwater management report which documents general information about the project as well the project’s RPv, Cv, and Fv compliance.

RPv compliance requires the performance of a Project Level DURMM (PLD) to determine a project’s volume shortfall. Additional information on conducting a PLD is provided on DelDOT’s ES2M Wiki. Compliance is demonstrated by comparing the results of the PLD to the individual DURMM runs developed for a project’s stormwater management BMPs. This information is typically displayed via an overall credit/debit table.

Cv and FV compliance can be evaluated through use of DelDOT’s Cv & Fv Compliance Flowchart and through use of any required hydrology and hydraulic (H&H) methods. The DelDOT Cv & Fv Compliance Flowchart outlines when Cv and Fv values are acceptable under different proposed conditions. It is important to note that meeting the requirements as shown on the flowchart does not release the designer from meeting other drainage requirements as outlined in Section 4.8.

A project’s Stormwater Management Report is to follow DelDOT’s standard Stormwater Management Report Format. All submissions, interim and final, should be provided electronically. The report should include all data, drawings, charts, maps, calculations, and explanations needed which lead to a clear understanding of the studies performed, methods and criteria used, results obtained, and conclusions reached. Though DelDOT provides a standard format, the design team should work with the Water Resources section during development so that the report format can be tailored to meet a project’s individual documentation needs.

4.9.3 Stormwater Management Facility Number Request

Department Resources
BMP identification form

A BMP identification form must be completed for each post construction stormwater management BMP proposed on the project. The form is completed by the design team and submitted to DelDOT’s Water Resources section. The BMP identification form assigns a final BMP number and outlines key data of the BMP like location, BMP type, facility dimensions, load reductions, etc.

4.9.4 BMP Design Guidance and Requirements

Department Resources
ES2M Wiki – Design Guidance
ES2M Wiki – Model Plans
Design Resource Center Example Plans

DelDOT is required to adhere to the requirements in the DSSR. Information within the DSSR, as well as additional supplementary design guidance related information, is also provided in DNREC’s Post Construction Stormwater BMP Standards and Specifications. DelDOT provides additional DelDOT specific BMP design guidance within its ES2M Wiki. DNREC has published Regulatory Guidance Memorandum RGM-1 that outlines the adoption of NOAA (National Oceanic and Atmospheric Administration) rainfall distribution curves.

All stormwater management BMPs should be clearly presented in the contract plans. Example Stormwater Management Plans are provided both on DelDOT’s ES2M Wiki as well as on DelDOT’s Design Resource Center. Additional information on plan presentation is included in Chapter 6.

4.9.5 Design Considerations

There are numerous stormwater management project development and design related considerations in addition to the requirements in the DSSR and additional guidance provided in DNREC’s Post Construction Stormwater BMP Standards and Specifications. This section outlines several common stormwater management considerations to ensure efficient project delivery and future intended BMP function. The topics included within this section should not be considered an all-encompassing list of pertinent project development and design-related considerations.

4.9.5.1 Soil Investigations

The DSSR requires varying levels of subsurface soil investigations based on BMP facility type. These soil investigations may be required to support the design or be performed during the construction phase to confirm assumed facility design parameters. The scope of the soil investigation required should be identified early in the project development process so that the required activities can be properly budgeted and scheduled. Required stormwater management soil investigation activities should be coordinated with other soil investigations to the extent practical. Additional guidance on soil investigation practices can be found in Section 4.14.2 and the methods for requesting the investigation can be found Section 3.7.10 [NEEDS LINK]. Refer to DNREC’s Post Construction Stormwater BMP Standards and Specifications for additional information on the level of soil investigations required.

4.9.5.2 Stormwater Management BMP Maintenance Access

Stormwater management BMPs require maintenance throughout their operational lives to provide their intended function. Accordingly, post construction maintenance for stormwater management BMPs in Delaware is prescribed in the DSSR. Additionally, the DSSR also prescribes specific maintenance access requirements. Beyond the prescribed requirements within the DSSR, consideration should be given to how DelDOT forces will access the BMP and their equipment needs to perform routine inspection, maintenance, repair, and rehabilitation activities throughout the life of the facility. The maintenance access routes must be designed to accommodate various maintenance tasks including mowing or use of other heavy machinery. In addition, there are various design elements that must be considered including barrier placement, slopes, and specific geometry of the site.

4.9.5.3 Stormwater Management BMP Facility Sequence of Construction

Proper stormwater management BMP construction sequencing balances the benefit of trapping sediment during construction with long term performance considerations for the facility. DelDOT provides

Department Resources
ES2M Wiki – SWM facility sequence of construction

suggested SWM facility sequence of construction for a few common stormwater facilities. These project notes are meant to be used as a guide and should be evaluated and altered as needed based on the circumstances associated with a specific project.

4.9.5.4 Shared Stormwater Management Facilities

In some cases, it may be advantageous for DelDOT to establish agreements with external entities to share stormwater management facilities for roadway and development use. In these cases, DelDOT is to establish joint use agreements which clearly describes ownership and future maintenance responsibilities. The potential need for these agreements should be identified as early as possible in the project development process and brought to the attention of DelDOT’s Water Resources section, NPDES Engineer, and Real Estate section. The DelDOT Water Resources section will not approve a project conveying stormwater to a BMP of which DelDOT does not possess adequate property rights without an executed stormwater agreement or confirmation of adjacent landowner to enter into a stormwater agreement concerning that BMP. DelDOT’s agreement development process is discussed in more detail in Section 5.2.3 [NEEDS LINK] and property rights are discussed in more detail in Section 5.5 [NEEDS LINK].

4.9.5.5 Select Watersheds in MS4 Permitted Areas

Department Resources
ES2M Wiki – Concurrence Meeting Agenda

DelDOT’s MS4 permits require additional water quality goals to be met in selected watersheds, above and beyond the requirements of the DSSR. DelDOT’s Concurrence Meeting Agenda identifies the selected MS4 watersheds with these additional water quality goals. Representatives from DelDOT’s NPDES Program may participate in the project’s stormwater management concurrence meeting at their discretion depending on the project’s scope to evaluate if additional water quality measures can be added to the project for MS4 compliance when the project occurs within these selected watersheds. Some potential adaptations may include, but are not limited to, upsizing a BMP for increased water quality crediting, including a stream or outfall restoration, adding soil amendments for enhanced pollutant reductions, or including a reforestation component. Adding such measures to a capital project is typically more economical than developing standalone project(s) for MS4 compliance. Additional information on MS4 permits is provided in Section 5.3.2.2.2.1 [NEEDS LINK].

4.10 Erosion and Sediment Control

Land disturbing activities, like DelDOT construction projects, expose bare soil surfaces which can lead to adverse impacts to the environment such as degradation of surface water quality, damage to adjacent land, and deterioration of aquatic habitat if not properly controlled through appropriate erosion and sediment control measures. Within Delaware, erosion and sediment control means the control of solid material, both mineral and organic, during a land disturbing activity, to prevent its transport out of the disturbed area by means of wind, water, gravity, or ice. There are various erosion stages including raindrop, sheet, rill and gully, and stream and channel. Similarly, there are various types of erosion and sediment control to manage these erosions. These controls can be either permanent, where they exist for the life of the facility, or can be temporary where they are used during construction, cleaning, or other activities.

Stormwater management as described in Section 4.9 and erosion and sediment control are intrinsically connected, as both address the interaction between water, soil, and land surfaces. Ineffective stormwater management can lead to increased runoff volumes and flow rates, which in turn exacerbate soil erosion and mobilize sediment along with other pollutants. In addition to their functional relationship, stormwater management and erosion and sediment control are also aligned through regulatory requirements. For instance, both DNREC and DelDOT require the integration of stormwater and erosion and sediment control planning into a single Stormwater Pollution Prevention Plan (SWPPP). A SWPPP must be prepared and approved prior to the commencement of any land disturbing activity, unless the project qualifies for an exemption.

Erosion and sediment control practices are governed by a combination of federal and state laws and regulations developed to protect water quality and minimize environmental impacts from land disturbing activities. Erosion and sediment control requirements in Delaware are contained in 7 DE. Admin. Code § 5101 which is commonly known as the Delaware Sediment and Stormwater Regulations (DSSR). The DSSR establishes the framework for managing stormwater and controlling erosion and sedimentation during construction and requires the development of a project specific erosion and sediment control plan that describes the relationship between the implementation and maintenance of erosion and sediment controls, including permanent and temporary stabilization and the various stages or phases of earth disturbance and construction for projects disturbing over 5,000 SF. As part of these regulations, the DNREC Erosion and Sediment Control Handbook is incorporated by reference and serves as a key technical guide for design and implementation of erosion and sediment control best management practices (BMPs). The handbook is supported by legal authority under 7 Del. C. § 4006(h) and (i). The DSSR and its regulatory authority and purpose are described in more detail in Section 4.9.

As described in Section 4.9, DelDOT is considered a delegated agency under the DSSR and is therefore responsible for ensuring that all projects comply with the requirements of the DSSR. Though many sections within DelDOT perform roles related to DelDOT’s maintenance of its delegated agency status, it is DelDOT’s Water Resources section that is tasked with directly overseeing many of the project development related components associated with DelDOT’s delegated agency status. The Water Resources section provides plan reviews and approvals, maintains technical resources and guidance, and is staffed with subject matter experts that can be consulted throughout the project development process.

4.10.1 Design Requirements and Guidance

Department Resources
Standard Construction Details
ES2M Wiki – DelDOT Erosion and Sediment Control Design Guide
ES2M Wiki – Mulching / E&S Guidance (2017)
ES2M Wiki
ES2M Wiki - Maintenance Only Projects

Erosion and sedimentation are accelerated through bare soil surfaces. Providing a vegetated or otherwise stabilized surface is critical in controlling erosion as it shields the soil surface from raindrop impact, provides a root system to hold soil particles in place, enhances the soil’s capacity to absorb water, reduces runoff velocity, and removes subsurface water between storm events through the process of evapotranspiration. A proper understanding of the existing and proposed conditions at a site is required so that control measures can be prescribed efficiently. Consideration should be given to understanding the hydrologic conditions of the site, identifying any environmentally sensitive areas, and determining and evaluating any temporary drainage patterns that will be created by the project.

During construction, the erosion and sediment controls must be maintained as prescribed within the project’s SWPPP. A Certified Construction Reviewer (CCR) will have scheduled walk-throughs to ensure control measures are properly installed and functioning correctly. Therefore, it is critical that erosion and sediment control measures be prescribed accurately during the design phase. DelDOT maintains several resources that can be used to supplement the requirements in the DSSR and in the DNREC Erosion and Sediment Control Handbook. Among those resources are the DelDOT ES2M Wiki, the Mulching / E&S Guidance (2017), and Erosion and Sediment Control Design Guide. DelDOT has additionally established details for several erosion and sediment control BMPs within the Standard Construction Details. DelDOT also provides separate guidance on Maintenance only projects on its ES2M Wiki.

4.10.1.1 Channel Lining Selection

Department Resources
ES2M Wiki – Channel Lining Selection Chart

The selection of a proper channel lining is an essential erosion and sediment control measure. The channel lining serves to protect the open channel from erosion, maintains structural integrity, and ensures long-term performance under varying flow conditions. Selecting the appropriate lining material is based on calculated shear stress values which are determined based on the slope of channel and depth of flow. Channel linings should be prescribed in accordance with DelDOT’s Channel Lining Selection Chart.

4.10.1.2 Pipe Outfalls

Department Resources
ES2M Wiki – Pipe Outfall Design Guidance for Scour Protection

Pipe outfalls, if not properly designed and protected, can create significant scour and erosion at discharge points. High-velocity flows exiting a pipe can rapidly erode the surrounding soil, undermine structures, and damage downstream channels or slopes. DelDOT provides guidance for prescribing pipe outfall protections through its Pipe Outfall Design Guidance for Scour Protection guidance posted on the ES2M Wiki. This resource provides guidance on when to prescribe outfall protection and on the type of scour protection to use. Additionally, drainage network discharge locations should be evaluated and considered in accordance with guidance provided in Section 4.8.3.3.

4.10.1.3 Limits of Disturbance over 20 Acres

7 DE. Admin. Code § 5101 (4.4) requires that no more than 20 acres be disturbed at any one time unless an exception is approved. This requirement necessitates the phasing of construction projects where over 20 acres are planned to be disturbed by the work. If an exception to this requirement is approved, site stormwater management BMPs are required based on the 2-year storm event with bare earth conditions.

4.10.2 Construction Phase Support

It is important for the design team to stay involved and support the project from an erosion and sediment control perspective once a project enters the construction phase. As a delegated agency, DelDOT will monitor the project site and evaluate the effectiveness of the erosion and sediment control measures and practices during the construction phase. It is often necessary for the original design team to assist in processing plan redlines or implementing revisions if issues or deficiencies are identified to ensure continued regulatory compliance and functional performance of the erosion and sediment control systems. The level of support required from the design team will vary by project.

4.11 Roadside Design

Department Resources
Clear Zone and Lateral Offset Application Discussion
DGM 1-30: Guidelines for Median Barrier on Divided Highways

The AASHTO Roadside Design Guide defines roadside design as the design of the area outside the traveled way. There are various features located within the roadside which serve different purposes. These features include but are not limited to roadway drainage facilities, highway signage, public or private utilities, bridge piers, sidewalk furniture, trees or other landscaping, and access to adjacent land uses. The AASHTO Green Book and AASHTO Roadside Design Guide establish the concept of lateral offset for vertical features so their presence does not adversely impact vehicles operating on the roadway and parked vehicles.

As described in Section 4.2, there are many design considerations associated with providing motorists with a high degree of safety within the traveled way. However, even when all applicable design criteria are met, there will be cases where motorists will leave the roadway and enter the roadside. Given the frequency and potential severity of roadway departures, it is essential to evaluate roadside safety as part of a project’s design process. The AASHTO Roadside Design Guide presents the latest national state-of-the-practice in roadside safety design. A key tenant of roadside safety design is that an errant vehicle should be provided a clear recovery area. This clear recovery area is commonly referred to as the clear zone and its suggested dimensions are provided in the AASHTO Roadside Design Guide. The AASHTO Roadside Design Guide also provides recognition that the clear zone defined within the guide may not be applicable to urban locations and therefore, introduces the concept of an enhanced lateral offset. DelDOT provides additional discussion on these concepts and their applications within its resource entitled Clear Zone and Lateral Offset Application Discussion.

Traffic barrier is commonly used in roadside design to shield obstacles but should not be placed indiscriminately. Instead, it should only be used where warranted and where striking the barrier is considered less hazardous than striking the obstruction which the barrier is meant to protect. The AASHTO Roadside Design Guide provides guidance on traffic barrier warrants and the traffic barrier applications that are available for use. In addition, DelDOT maintains DGM 1-30 entitled Guidelines for Median Barrier on Divided Highways which establishes DelDOT’s practices for installing median barrier on access-controlled and non-access controlled divided roadways in Delaware.

Roadside safety design requires a careful consideration on the benefit and cost of improvements at the project level, given the finite budgets and resources available to make transportation improvements. In general, it is more cost-effective to include roadside improvements on new construction or major reconstruction projects (4R projects), as these projects offer the greatest opportunity for implementing roadside enhancements. As highlighted in the AASHTO Roadside Design Guide, roadside improvements are to be considered commensurate with the project’s scope. Providing for the highest level of roadside design criteria on all projects, regardless of cost or safety effectiveness, may divert resources from other projects or initiatives which can result in system-wide safety remaining static or even being degraded.

4.11.1 Utilities

Public utilities are commonly accommodated within the public right-of-way due to their societal benefits; however, the accommodation of utilities within the public right-of-way may result in the addition of facilities that act as roadside obstacles. The federal regulations dictating the accommodation of utilities in the right-of-way in relation to the clear zone on Federal-aid projects is included in 23 CFR 645.209. 23 CFR 645.209(b) requires that no new above ground utility be placed inside of the established clear zone of the highway unless a determination has been made by the project team that placement underground is not technically feasible or is unreasonably costly and there are no feasible alternate locations. In cases where new aboveground utilities are permitted, they are to be located as far from the traveled way as possible, preferably along the right-of-way line. 23 CFR 645.209(a) notes that the lack of sufficient right-of-way width to accommodate utilities outside the desirable clear zone, in and of itself, is not a valid reason to preclude utilities from occupying highway right-of-way on Federal-aid projects.

Delaware’s regulations dictating the accommodation of utilities in the public right-of-way in relation to a project’s clear zone is contained in 2 DE. Admin. Code § 2401 (4.5.2.3). The administrative code requires that aboveground utility facilities be placed consistent with the project’s clear zone. If the project’s utilities cannot be placed consistent with the project’s clear zone, then the feature is to be made breakaway unless placed as close to the public right-of-way line as feasible.

Additional information on the utility coordination process is included in Section 5.4 [NEEDS LINK].

4.12 Value Engineering

Department Resources
Policy Implement D-05: Value Engineering
Construction Manual

DelDOT, like other transportation agencies, has limited funding available for delivering its transportation program. For this reason, it is important that project costs be judiciously considered at the project level. In general, as the cost of a project increases, so does the potential savings realized by critically assessing the project to optimize value. 23 CFR 627.1 requires that states establish and maintain a program to perform value engineering analyses as part of a state’s typical project development process. DelDOT’s policy for performing value engineering analyses is established in Policy Implement D-05 entitled Value Engineering. For purposes of this manual, a value engineering analysis is a systematic process of reviewing and assessing a project by a multidisciplinary team, with no prior direct project involvement, to provide recommendations for achieving the project’s needed function while also considering community and environmental commitments, safety, reliability, efficiency, and overall life-cycle cost in a manner which optimizes the value and quality while reducing project delivery time.

DelDOT’s value engineering program is administered by the Engineering Support section; however, it is the design team’s responsibility to monitor and assess a project throughout its life and determine whether a value engineering analysis is required or would otherwise be beneficial in accordance with the Selection of Projects criteria defined in Policy Implement D-05. There is no federal allowance to waive the performance of a value engineering analysis for a Federal-aid project on the National Highway System (NHS) or major projects as defined by 23 U.S.C. 106(h). Therefore, to ensure that unexpected costs don’t create late project development exceedance of these threshold amounts, it is DelDOT best practice to conduct a value engineering analysis for Federal-aid projects on NHS routes with projected total costs of all funding phases at or above $35 and $45 million dollars for bridge and roadway projects, respectively. The performance of a value engineering study may be waived when the project is not on the NHS and is only using state funding in accordance with Policy Implement D-05. The specific roles, responsibilities, and processes for conducting a value engineering analysis are contained in Policy Implement D-05.

The timing of the value engineering analysis is critical to achieving the benefit of the study, and there is flexibility on when the analysis can occur within the project development phase. 23 CFR 627 and DelDOT Policy Implement D-05 only require the performance of a value engineering analysis prior to final design and all approved recommendations incorporated prior to the project’s PS&E. 23 CFR 627 encourages conducting the value engineering analysis as early as practicable in the project development process but also provides recognition that their timing should be closely coordinated with other project development activities to minimize the impact approved recommendations might have. The decision on when to conduct the value engineering analysis within the project development process is ultimately left to the discretion of the design team. This decision must consider the time it takes to prepare for, conduct, and implement approved changes. Policy Implement D-05 provides additional considerations and alternatives related to the timing of the value engineering analysis within the DelDOT project development process.

Where a value engineering analysis is required by Policy Implement D-05 or otherwise desired for a project using the design-build project delivery method, the value engineering analysis is to be conducted on the request for proposals document or other applicable solicitation documents. CM/GC projects that meet the Selection of Projects criteria in D-05 are required to have a value engineering analysis completed and approved recommendations incorporated into the contract documents prior to requesting a construction price from the CM/GC contractor in accordance with 23 CFR 627. Alternative contracting methods are discussed in more detail in Section 6.1 [NEEDS LINK].

Contractors are permitted to submit value engineering proposals during the construction phase in accordance with DelDOT’s standard contract language. The review process and the handling for these value engineering proposals are detailed in DelDOT’s Construction Manual.

4.13 Resiliency and Sustainability

Department Resources
[1]

Integrating resiliency and sustainability principles into the design of transportation facilities has become an increasing point of emphasis for DelDOT and other transportation agencies across the country to combat the effects of climate change and associated sea level rise and flooding. Proactively incorporating resiliency and sustainability considerations into the DelDOT project development process enhances public safety, strengthens and protects infrastructure, and supports the long-term viability of the transportation network. DelDOT’s Resiliency and Sustainability section was created to centralize DelDOT’s efforts to improve the resiliency of DelDOT’s transportation network and refine its focus on sustainability.

In general, there is no one size fits all design solution for incorporating resiliency and sustainability practices into a project; instead, incorporation usually consists of striking a balance between economic, social, and environmental factors in a manner that supports the ongoing planning, development, operation, and maintenance of an ‘enduring’ transportation system. Design considerations directly related to resiliency and sustainability include roadway and bridge elevations, roadway and roadside materials, strengthening bridges against scour, designing drainage systems capable of handling increased precipitation, and overall system planning for future transportation facilities. The Resiliency and Sustainability section is actively developing design guidance that will be incorporated into this manual as it becomes available.

There are several tools available that can assist the design team make informed judgements on how sea level rise will affect their project. Several of these tools are summarized in Table 4.13. Additional information on Resiliency and Sustainability is included on DelDOT’s Resilience and Sustainability website and in Delaware’s Climate Action Plan.

Table 4.13 – Sea Level Rise Tools

Tool	Link
Delaware Flood Planning Tool	https://floodplanning.dnrec.delaware.gov/
NOAA SLR GIS Viewer	Sea Level Rise and Coastal Flooding Impacts

4.14 Materials

Department Resources
Materials Manual

The use of quality materials to construct a project helps ensure a lasting product with reduced future maintenance requirements. In addition to the quality of the materials, it is also important to consider the environment in which the material will be placed to enable intended performance. DelDOT’s Materials and Research section is staffed with experts that oversee DelDOT’s materials related programs and processes. Among the project development related functions that the section oversees includes:

• Administering a material quality assurance program that meets the requirements of 23 CFR 637 for Federal-aid Highway Projects, which consists of testing materials at project sites and production facilities for compliance with specifications and plans,
• Providing existing site investigative services including performing soil borings, pavement cores, and pipe video inspection,
• Recording and maintaining information related to material usage on DelDOT contracts and Department issued permits and agreements,
• Performing pavement design and providing pavement structure recommendations,
• Providing recommendations concerning the suitability of materials to be utilized during construction,
• Approving material sources of supply prior to construction, and
• Maintaining approved material lists.

This section outlines several material related project development considerations that should be evaluated by the design team. Additional information on the Materials and Research section is included in DelDOT’s Materials Manual. It is noted that DelDOT follows the same material quality assurance program procedures regardless of funding source.

4.14.1 Pavement Design

Pavement design is one of the key functions that is performed by DelDOT’s Materials and Research section. Discussion on the considerations associated with pavement design is included in Section 4.2.2.

4.14.2 Subsurface Strata Investigation

Subsurface strata investigations are typically referred to as soil borings. Soil borings provide information on the physical and mechanical properties of soil to assess its suitability for different purposes as well as detects for the presence of groundwater. The performance of soil borings is needed for the design of certain transportation infrastructure as described within this manual.

There are numerous procedures and techniques available for obtaining subsurface strata information and in-situ samples. The level and type of investigation required is dependent on many factors including previous investigations performed in the area and the elements of the proposed design. The Materials and Research section will work with the design team to determine the level of subsurface investigation that is needed on an individual project.

Additional information on requesting soil borings is contained in Section 3.7.10 [NEEDS LINK]. Soil borings can either be performed through DelDOT’s on-call drilling agreements or other professional service agreements. This section summarizes DelDOT’s recommended subsurface strata investigation practices which have proven successful in this state. These practices are to be followed unless agreed upon otherwise by the Materials and Research section. Following these practices will ensure uniform sampling, testing, and documentation across DelDOT’s various programs.

4.14.2.1 Soil Boring Practices

Department Resources
DOH-19

Soil borings should be performed at the planned locations; however, there may be instances where field conditions will not permit boring at the planned location. When conditions do not permit drilling at the planned location, the soil boring may be relocated within a 20-foot radius of the planned location after concurrence is received from the DelDOT Geotechnical Engineer.

Soil borings for signal foundations should be requested to a depth of 40 feet unless there are extenuating circumstances. Deviations from the recommended 40-foot depth should be confirmed by DelDOT’s Geotechnical Engineer.

Strata encountered is to be visually and manually classified in accordance with the procedures contained in DOH-19. Soil samples obtained are to be carefully handled to ensure that the material is as undisturbed from site conditions as feasibly possible. Soil samples obtained during a subsurface investigation are put in airtight bags to preserve the moisture and fine material contents.

Soil strata exploration is to adhere to the following practices:

• Continuous sampling for the top 20 feet of boring,
• Standard Penetration Testing (SPT) in 5 feet intervals thereafter,
• n-Value determined in 6-inch intervals with 24-inch spoon, and
• 140 lb. hammer dropped 30 inches.

If rock is encountered, it must be noted on the boring log. Sample length, recovery, rock quality designation (RQD) to the nearest percent, and description must be recorded. Rock samples are to be cataloged and photographed with measurements in the sample boxes before handling or being disturbed. Rock samples must be stored by the design team or driller during the design phase and turned over to the Delaware Geological Survey at the University of Delaware after design is complete.

Stormwater related investigations are to follow the applicable requirements of 7 DE. Admin. Code § 5101. Test results are to be submitted to the DelDOT Geotechnical Engineer and the DelDOT Water Resources Engineer.

4.14.2.2 Soil Boring Testing and Reports

Once the field work is complete, the collected soil samples will be tested, and all collected field and laboratory obtained information will be compiled into various reporting formats. This section describes the reporting and testing information that is to be compiled. When drilling is performed under professional service agreements other than the DelDOT on-call drilling agreements, all the following are to be submitted to the DelDOT Geotechnical Engineer:

• Boring logs,
• Associated drilling logs,
• Laboratory analyses,
• Location plans, and
• Geotechnical reports.

4.14.2.2.1 Boring Logs

Boring logs are used to summarize the soil boring exploration. Boring logs submitted to DelDOT must include the following information at a minimum:

• Project number.
• Project name.
• Boring number with unique identifier. Do not use B-1 or SB-1 on every project. The boring log number is to be job specific, for example Dupont Highway Boring #1 could be DH-1.
• Northing and easting of each boring.
• The model of drilling rig being used.
• Names of the driller, logger, and any helpers.
• The date the boring is started and the date of completion.
• Sample recovery in inches for each sample as well as the 4 blow counts per spoon.
• Depth water is encountered, depth of water at completion, and depth the hole caved.

4.14.2.2.2 Laboratory Testing

All recovered samples are to be tested, not just select samples or locations of strata changes. Material description and classification is to be performed in accordance with the AASHTO classification system and not with the Unified Soil Classification System (USCS). All requested laboratory testing must be completed by an AASHTO accredited laboratory certified in the scope of the requested material testing. The standard laboratory soil testing to be performed on collected samples includes the following:

• Moisture content in accordance with AASHTO T265 Standard Method of Test for Laboratory Determination of Moisture Content of Soils,
• Particle Size of Soil in accordance with AASHTO T88 Standard Method of Test for Particle Size Analysis of Soils,
• Liquid Limit of Soil in accordance with AASHTO T89 Standard Method of Test for Determining the Liquid Limit of Soils,
• Plastic Limit of Soil in accordance with AASHTO T90 Standard Method of Test for Determining the Plastic Limit and Plasticity Index of Soils, and
• Organic content in accordance with AASHTO T267 Standard Method of Test for Determination of Organic Content in Soils by Loss on Ignition.

Additional testing may be requested when determined necessary for the project. These additional tests should be coordinated with the DelDOT Geotechnical Engineer.

4.14.2.2.3 Soil Boring Report

Once the field work is complete and all collected samples are analyzed and tested, the results of the soil boring investigation will be documented into a Soil Boring Report. The Soil Boring Report summarizes all field data and laboratory test results. Soil Boring Reports generated by the DelDOT Geotechnical Engineer will include the following:

• Soil profile data summary showing the sample location, depth of recoveries, soil profile description, soil classification using the AASHTO classification system and any remarks. The soil samples are tested, and a summary of this analysis is included in the report.
• Based upon the subgrade soil characteristics, the report may provide recommendations for muck excavation, limits of special fill, recommendation to eliminate underdrains, grade adjustments, embankment construction, and the use of geotextiles or other special construction considerations.

4.14.3 Material Specifications and Testing

All material related specifications and testing requirements that are either added to or which otherwise modifies DelDOT’s standard requirements should be reviewed by DelDOT’s Materials and Research section for accuracy and contract conformity.

4.14.4 Domestic Material Preference Requirements

Department Resources
Buy America Guidance Website

Projects that use federal financial assistance for infrastructure are required to meet the domestic material preference requirements contained in 2 CFR 184. This regulation requires that all defined construction materials, manufactured products, and iron or steel products be produced in the United States. Additionally, projects that use Federal-aid Highway Program funds are further required to comply with the domestic material requirements contained in 23 CFR 635.410, which slightly alters the domestic material preference requirements for iron and steel materials and for certain manufactured products.

23 U.S.C. 313(h) applies the domestic material preference requirement to all work eligible for federal assistance within the scope of the National Environmental Policy Act (NEPA) approval regardless of funding source utilized for such work. This means that all work eligible for reimbursement under an action, such as utility work, must meet the domestic material preference requirements. The design team can apply for a waiver to the domestic material preference requirements; however, applying for a waiver and the processing of the waiver requires significant time. Therefore, the design team should consider atypical material needs, including those of reimbursable utilities, as early as feasible in the project development process to determine whether a waiver may be required or if redesign to avoid the impact is feasible. DelDOT maintains a website which summarizes the federal domestic material requirements as well as provides guidance which has been developed by DelDOT.

4.14.5 Patented and Proprietary Products

DelDOT and other State DOTs are permitted to specify patented and proprietary products within its projects in accordance with 84 FR 51023. This Final Rule removed the previous requirement for state DOTs to perform a Public Interest Finding prior to specifying a specific patented or proprietary product within a contract. Though DelDOT is permitted to prescribe specific patented or proprietary products, its use should be measured and reserved to applications which require the specific features that only a certain product can meet. When a specific patented or proprietary product is to be specified, its ability to be sourced domestically must be considered in accordance with Section 4.14.4 [NEEDS LINK].

4.14.6 State Furnished Material or Equipment

Contracts which use Federal-aid Highway Program funding require that the awarded contractor furnish and select the sources of all material that is to be incorporated into the work. However, in certain situations, it may be advantageous for the State to prescribe incorporation of specific materials. Materials that are required for use on a contract which are to be furnished by the State require a Public Interest Finding. A common application of state furnished materials incorporated into a transportation project is a borrow source made available and prescribed for use by the State. When DelDOT requires the use of a state furnished material, the contract must state the location of the material and the price to the contractor. Additional information on incorporating state furnished materials is included in 23 CFR 635.407.

The requirement to use state or other publicly owned equipment should generally not be included in a contract that is to be advertised with federal funds; however, there may be cases where the use of public equipment is warranted or justified. In these cases, the use of publicly owned equipment must be demonstrated to be cost effective under the particular project conditions or locality and must meet the conditional requirements established in 23 CFR 635.106.

4.14.7 Earthwork Material Usage and Stockpiling

Earthwork is the generic term assigned to all work and materials required to construct excavated areas and embankment areas on a project. Properly constructed earthwork provides a well-draining and stable foundation for all other road and bridge related work. Specifying the appropriate earthwork materials, accounting for sufficient and separated stockpile areas, and accurate material quantification are all important design phase tasks within the project development process.

The Materials and Research section can provide technical input to the design team on specifying appropriate embankment material for a contract. Embankment soil can be composed of either common material or select material defined as follows:

• Common material – Material that is not suitable for use as select material but is suitable for less critical areas. Common material is referred to in the Standard Specifications as Class F and must meet the requirements of Section 1001.
• Select material – Material that is graded and tested to conform to designated specifications. A high-quality granular soil used for backfilling structures, constructing roadway bases, and for other significant applications. Select material is referred to in the Standard Specifications as either Class A, B, or C and must meet the requirements of Section 1001.

In general, sources of suitable excavated material should be exhausted before importing offsite material. Excavated soil should be separated and stockpiled according to its classification. Offsite soil that is imported to a project site is referred to as borrow. To be able to calculate any required borrow amounts, it is necessary to have a general understanding of the quality and condition of the existing on-site material. The Materials and Research section can employ various site exploration techniques to obtain information about the existing on-site material to assist the design team make informed decisions.

4.14.8 Precast Concrete and Structural Steel

DelDOT’s Materials and Research section performs in-plant inspections of precast concrete and structural steel elements as part of DelDOT’s material quality assurance program. The Materials and Research section will typically fund these inspections from its own budget; however, consideration should be made on large projects to having the inspection costs fully or partially covered by the project’s funding so as not to deplete the Materials and Research section’s funding. The design team should proactively update DelDOT’s Materials and Research section on upcoming planned work involving non-standard precast concrete items as well as structural steel to enable informed Department budgeting and resource allocation.

4.15 Landscaping

Department Resources
Enhancing Delaware Highways Manual

Landscaping can enhance the roadside and add aesthetic value to a project; however, there are many design and practical considerations that must be evaluated when landscaping is prescribed within a DelDOT project to ensure intended and lasting results. For the purposes of this section, landscaping refers to any plantings or vegetation outside of DelDOT’s typical grass seeding applications. Landscaping can be placed both within operational right-of-way and on state-owned property. Landscaping can be included on a project for a variety of reasons, such as to:

• Create an aesthetic feature which enhances the roadside to be visually appealing to both road users as well as adjacent properties.
• Meet the requirements of 17 Del. C. § 201 et seq., commonly referred to as the Delaware Tree Bill. See Section 5.3.2.2.2.7 [NEEDS LINK] for additional information on the Tree Bill and its requirements.
• Provide soil stabilization in areas where turf grass may not be a suitable option such as on steep slopes, along shorelines, streambanks, and other grounds adjacent to waterways.
• Act as a vegetative visual screen and a stewardship effort as part of the public involvement process.
• Provide privacy or protection from headlight glare.
• Meet the regulatory requirements for certain stormwater management BMPs.
• Create habitat as a stewardship effort or mitigation for specific project impacts or future project impacts.
• Act as a pedestrian traffic deterrent.

The inclusion of landscaping on a project will require coordination with various sections within DelDOT. Sections which may require coordination, as well as their delegated role within the design process, are described as follows:

• Roadside Environmental group – This group is a part of DelDOT’s Maintenance and Operations Division and should be consulted whenever landscaping is planned on a project. For projects developed by DelDOT staff, the Roadside Environmental group will perform the landscaping design and provide the result to the design team for inclusion into the contract. For projects developed under professional service agreements, the group will review the landscaping plans to ensure adherence to applicable laws and regulations as well as other standard DelDOT practices. To be able to perform their role, the group must be provided information on project location, expected planting season, the intent of the landscaping, anticipated DelDOT maintenance responsibilities, and any other project specific information pertinent to the project’s landscaping.
• Water Resources section – This section should be consulted any time when landscaping will be utilized as an alternative to traditional turf grass soil stabilization.
• Environmental Stewardship Office – This section should be consulted whenever landscaping is being used as a way for DelDOT to meet its stewardship and mitigation obligations. This includes but is not limited to landscaping required by the Delaware Tree Bill, creation of a visual screen as part of the public involvement process, creation of habitat, or mitigation for a specific project impact or future project impact, such as wetlands.
• Maintenance and Operations – The appropriate DelDOT Maintenance and Operations district should be consulted when the planned landscaping is included within DelDOT operational right-of-way. The district can provide input on preferred access and plants as well as other maintenance-related considerations.
• Land Services group – This group is included within DelDOT’s Right-of-Way section. The Land Services group manages and oversees the maintenance of excess lands for DelDOT. Consultation with this group should occur when the planned landscaping is included on a parcel outside of the State’s operational right-of-way.
• DelDOT Legal section – This section must be consulted whenever an agreement is required as part of the landscaping design process.

Landscaping can either be performed within the infrastructure project necessitating the planting or can be broken into a separate standalone landscaping contract. The benefits and disadvantages should be discussed as a project team. When landscaping is separated into a standalone project, the project team must ensure funding availability especially in cases where the landscaping is needed to meet regulatory requirements or when public commitments have been made. Additionally, there are several other design and project-level considerations that must be evaluated when prescribing landscaping, including but not limited to, the following:

• The implication to roadside safety as certain landscaping can constitute a roadside obstacle to the public.
• The effect to sight distance, especially if the landscaping is located along the inside of a curve or near the intersection of roadways.
• Future maintenance responsibilities. This will require coordination with all stakeholders and may necessitate the development of a maintenance agreement in situations where DelDOT will either share maintenance responsibilities or otherwise delegate responsibility to another agency. Additional information on the process for developing agreements is provided in Section 5.2.3 [NEEDS LINK].
• The proximity of landscaping in both the planted and future condition to other features such as utilities, sidewalks, drainage features, and the roadway to ensure an appropriate offset is provided.

Additional information related to landscaping and its considerations are included within DelDOT’s Enhancing Delaware Highways Manual.