Design

Frequently Asked Questions

The Federal Highway Administration (FHWA) has noted and appreciates what a number of States are doing in the area of practical design and related strategies. Several analytical tools are now available, such as the Highway Safety Manual (HSM), Interchange Safety Analysis Tool (ISAT), Road Safety Audits (RSA), and Interactive Highway Safety Design Model (IHSDM), which support and enable the practical design approach. FHWA thinks this approach has a good deal of potential, particularly in a performance-based environment. FHWA is exploring the role it can play in helping to promote, advance, and facilitate performance-based practical design (PBPD) and how FHWA can best position its division offices and State agencies to be receptive to PBPD's use. The following questions and answers help further define and illustrate the current understanding of the PBPD concept.

1. What is Practical Design?
2. Where can I find more information about State Practical Design practices?
3. What is PBPD and how does it differ from Practical Design?
4. How does PBPD differ from what agencies are currently doing?
5. Where does PBPD apply in the planning and project development process?
6. What is an example of a PBPD decision?
7. Does PBPD apply equally to all types of roadways and all types of projects?
8. Is PBPD only for design?
9. What is meant by a design-up approach?
10. How does PBPD help with flexibility in design?
11. How can performance-based analysis be used to support project-level decisions?
12. What are the types of safety and operational analytical tools that can be used in PBPD? What tools would be appropriate?
13. Does PBPD negate the need to use existing design standards or guidelines previously used for design projects?
14. Does PBPD affect Americans with Disabilities Act (ADA) or Section 504 of the Rehabilitation Act requirements?
15. Does PBPD eliminate the need for design exceptions?
16. How does a PBPD approach change existing procedures for requesting and approving design exceptions?
17. What is the relationship between a project's purpose and need and PBPD?
18. What is the relationship between PBPD, context-sensitive solutions, and livability?
19. What is the relationship between PBPD and value engineering?
20. Will PBPD create any new planning or National Environmental Policy Act related requirements?
21. What impact might PBPD have on right-of-way acquisition?
22. How does PBPD relate to asset management?
23. Will PBPD result in multimodal needs, such as pedestrian and bicyclist needs, being eliminated from projects?
24. Can/should PBPD result in a project that is less safe than the existing condition?
25. What are the challenges of implementing a PBPD process?

1. What is Practical Design?

   There isn't one definition for Practical Design. Each State using the term has a somewhat different definition, and some States may use other terms for similar approaches. Agencies with a Practical Design or related policy "have a common goal—developing individual projects cost-effectively to meet only the project's purpose and need and applying cost savings for additional projects, thereby optimizing their budgets statewide" (NCHRP Synthesis 443 (.pdf), p. 33).

2. Where can I find more information about State Practical Design practices?

   NCHRP Synthesis 443: Practical Highway Design Solutions (http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_syn_443.pdf (.pdf)) summarizes a survey of States about practical design and describes the practical design practices in six States.

3. What is PBPD and how does it differ from Practical Design?

   Practical Design is a renewed focus on project scoping to strictly address purpose and need, while PBPD enhances the grounding of these decisions in a performance-management framework. A concern with Practical Design is that agencies may overemphasize short-term cost savings without a clear understanding of how such decisions would impact other objectives (e.g., safety and operational performance, context sensitivity, life-cycle costs, long-range corridor goals, livability, and sustainability).

   Agencies using a PBPD approach have specific long- and short-term performance goals that can apply to a project, a whole corridor, or the overall system. Using available performance-analysis tools and qualitative assessments, these agencies create projects that include only those features that serve the long- and short-term performance goals. Projects do not need to include features that provide performance exceeding the stated goals, fail to serve those goals, or are inconsistent with the purpose and need.

4. How does PBPD differ from what agencies are currently doing?

   Many States routinely practice elements of PBPD (even though they may not call it PBPD) with the goal to deliver maximum value at lower cost by improving the project development decision making process. With the emergence of new and improved performance analysis tools, PBPD is now more efficient to apply and information from these tools is more reliable. Agencies that adopt a PBPD philosophy will continue to analyze project development decisions and tradeoffs, but will emphasize the need to use quantitative performance information to support decision making. PBPD will help agencies accelerate improvements to the system by selecting projects and project elements that provide performance value.

5. Where does PBPD apply in the planning and project development process?

   The PBPD approach begins at the planning and scoping phases and doesn't just look at a single project. It is a holistic approach, looking at the entire transportation system. An emphasis of PBPD is on the planning-level corridor or system performance needs and objectives when planning, scoping and developing individual solutions.

   As agencies struggle with funding limitations, they need to make sure the purpose and need for the actual project action is well defined and adhered to during not only the early stages of planning and project development but also throughout the preliminary and final design of the project.

6. What is an example of a PBPD decision?

   In addressing a clearly defined purpose and need of a project to add capacity to a rural two-lane highway, an agency initially considered a four-lane divided highway cross-section over the entire length of the corridor. As part of the evaluation of alternatives in the National Environmental Policy Act (NEPA) process, the agency conducted both operational and safety analyses. The operational analysis revealed that improving the two-lane highway to a three-lane section with alternating passing lane sections could satisfy the anticipated demand for the desired service life of the project. Results of the safety analysis indicated that the three-lane alternative could reduce fatal and serious injury crashes by approximately 20 percent per mile as compared to the existing condition. This three-lane alternative significantly reduced the project footprint and associated impacts while improving safety and operational performance. This alternative also can be programmed for construction several years sooner than originally anticipated because it greatly reduces the impacts to environmentally sensitive resources and the time needed to complete the NEPA process. In this scenario, through the NEPA process, the agency identified the three-lane alternative as the preferred alternative for most cost effectively achieving the purpose and need.

   By evaluating the performance value of alternatives and applying PBPD early, the agency has created an opportunity for savings that can be used to serve other needs and priorities. This could include using the anticipated savings to add bike lanes and sidewalks to the entire length of the project, or alternatively, to increase the project length by several miles to address safety and operational needs of the corridor, or do neither and apply the savings to another project that has more critical needs.

7. Does PBPD apply equally to all types of roadways and all types of projects?

   Yes, PBPD can be successfully applied across a broad range of roadway and project types, from new construction to preventive maintenance.

8. Is PBPD only for design?

   No. PBPD is a philosophy of balancing project purpose and need with design for all users and life-cycle costs. To gain the greatest benefit from PBPD, practitioners are highly encouraged to take a system-wide perspective and incorporate PBPD concepts into all decisions related to planning, programing, and project development. Starting at the planning and programming phase, a multi-disciplinary group can weigh the options and trade-offs to define a focused project purpose and need and performance goals that are used throughout the life of the project.

9. What is meant by a design-up approach?

   Using a traditional design approach, there are a few, key design choices that will dictate much of the form and function of a project. These choices create design controls and include the functional class, design traffic volume, design speed, design vehicle and design user. There may be other design constraints that are outside of a designer's control and could include the right-of-way constraints, environmentally sensitive resources, terrain, weather and setting (rural, suburban, and urban) for the project location. Once the design controls for a project are known, they lead the engineer to numerous standards for the roadway elements. Once established, designers can better understand which of these standards will be difficult to meet due to various reasons and constraints.

   The designer choosing to use a design-up approach rooted in PBPD will first consider the project purpose and need based upon explicitly defined transportation performance needs. Subsequently, the designer will also consider social, natural, and environmental constraints for a location. The designer then will begin to select and size project design elements that directly serve the transportation performance needs while working within constraints and minimizing impacts to important resources. The design-up approach then evaluates how the preliminary design layout compares to the applicable design controls and related standards for the project's location and context, and evaluates whether to modify individual elements in order to better meet standards, and documents the decisions accordingly. These decisions consider the costs verses the performance benefits of modifying a design element to meet a standard.

10. How does PBPD help with flexibility in design?

    Flexibility in design (as discussed in the American Association of State Highway and Transportation Officials' (AASHTO) - A Guide for Achieving Flexibility in Highway Design [May 2004] and the Federal Highway Administration's (FHWA) - Flexibility in Highway Design [1997]) helps agencies deliver solutions that balance safety and mobility for all users with the preservation and enhancement of community and environmental resources. PBPD can broaden this approach by including a greater focus on expending resources only as needed, as determined by performance goals and evaluation, and relating project decisions to the opportunity cost to other projects, corridors, or the overall network.

    Critical to achieving that balance is understanding the relationship between the design features of a roadway and how these features relate to performance. Designers use this knowledge to:

    • Evaluate the extent to which a design meets (or does not meet) project goals or objectives;
    • Assess the likelihood and significance of performance impacts; and
    • Identify appropriate mitigation strategies that address performance concerns.
11. How can performance-based analysis be used to support project-level decisions?

    Performance-based analysis provides a quantifiable comparison of geometric design options in support of a benefit-cost analysis. Performance-based analysis also helps prioritize planning and project-level decisions, and it provides data to determine whether the project's purpose and need have been met.

    The range of potential performance impacts of design decisions is generally larger early in the project development process because the range of design options is broader early in the process (e.g., a two-lane versus a four-lane facility) and narrows with each successive decision throughout the process (e.g., 11-ft versus 12-ft lanes). Performance-based analysis provides a basis for objectively assessing the relative contribution of each decision to the project purpose and need.

12. What are the types of safety and operational analytical tools that can be used in PBPD? What tools would be appropriate?

    Several tools are now available that enable a wide variety of performance analyses to be conducted. The tools available range from simple to complex and can be scaled to fit a wide range of geometric design scenarios. These tools can model existing conditions or predict future conditions. The most appropriate type of tool to be used for a particular analysis will be based upon the following factors:

    • The stage of the project development process (i.e., planning, preliminary design, or final design).
    • The availability and quality of pertinent data.
    • The complexity of the design (e.g., rural versus urban, or single lane versus multi-lane).

    For analyzing safety performance, refer to the 2010 AASHTO Highway Safety Manual (HSM) and FHWA's HSM website (http://safety.fhwa.dot.gov/rsdp/hsm.aspx).

    For analyzing operational performance, refer to the Highway Capacity Manual and FHWA's Traffic Analysis Tools website (http://ops.fhwa.dot.gov/trafficanalysistools/index.htm).

13. Does PBPD negate the need to use existing design standards or guidelines previously used for design projects?

    No. Existing policies and guidelines (e.g., the AASHTO Green Book and State design manuals) contain valid principles for design that provide the practitioner with useful information for making an informed decision using engineering judgment. The designer needs to bear in mind that in many cases, these resources are intended to guide the decision-making process, not dictate a particular solution. In that sense, design guidelines are consistent with PBPD goals.

14. Does PBPD affect Americans with Disabilities Act (ADA) or Section 504 of the Rehabilitation Act requirements?

    No. Pedestrian facilities must be made accessible for all users when those facilities are constructed or altered. Additional information on accessibility is available at: https://www.fhwa.dot.gov/accessibility.

15. Does PBPD eliminate the need for design exceptions?

    No. PBPD can be implemented with the flexibilities already available within FHWA regulations, standards, and policies, as demonstrated by States that currently have practical design policies. Design exceptions are a means of evaluating, documenting, and approving decisions to select a value outside of established design standards.

16. How does a PBPD approach change existing procedures for requesting and approving design exceptions?

    Design exceptions are a useful tool for employing practicality and flexibility in design decisions in a design-up approach. Implementation of PBPD should not necessitate changes in the existing procedures for requesting and approving design exceptions. As described in the FHWA Mitigation Strategies for Design Exceptions, an effective design exception process includes the following tasks:

    • Determine the costs and impacts of meeting the design criteria;
    • Develop and evaluate multiple alternatives;
    • Evaluate risk;
    • Document, review, and approve exceptions; and
    • Monitor and evaluate in-service performance.

    Under existing design exception procedures, agencies could include system-wide costs, benefits, and risks in the development, evaluation, and justification for approval of design exceptions. Evaluation of risk is a key feature that is common to both design exceptions and PBPD.

17. What is the relationship between a project's purpose and need and PBPD?

    The first fundamental step in the overall project development process is defining and having a clear understanding of the purpose of and need for a project. Transportation professionals and stakeholders focus on the identified needs and commit the appropriate resources. As transportation decision-makers struggle with funding limitations, it is more imperative than ever that the purpose of and need for the actual project action are well-defined and adhered to—not only during the early stages of project development but also throughout the preliminary and final design of the project. PBPD is rooted in a strong focus on the purpose and need.

18. What is the relationship between PBPD, context-sensitive solutions, and livability?

    Context-sensitive solutions (CSS) and livability seek a transportation solution that addresses the needs of all road users and the functions of the facility within the context of its setting, considering land use, users, the environment, and other factors. CSS is a collaborative, interdisciplinary approach that includes the viewpoints of all stakeholders in the development of a shared vision of project goals, and uses a defined decision-making process. CSS, livability, and PBPD rely on flexibility to achieve results that meet the project purpose and need. PBPD compliments CSS and livability by providing performance information that supports decision-making.

19. What is the relationship between PBPD and value engineering?

    PBPD is not the same as value engineering (VE), but the PBPD philosophy and VE process are complementary. A VE is an analysis of materials, processes, and products from which a selection may be made to achieve the required function at the lowest overall cost, consistent with the requirements for performance, reliability, and maintainability. PBPD is the overarching approach that guides planners, programmers, and engineers to focus on performance improvements that benefit both project and system needs.

    PBPD and VE share the similar goal of achieving the greatest benefit-to-cost ratio; however, VE typically focuses on the decision within a single project, while PBPD considers the decision within the context of improving the overall system. Even though VE is required on Federal-aid projects that meet certain criteria by having an independent group conduct a review and report on the findings, all projects can benefit by adopting the philosophy of both VE and PBPD throughout the project development process.

20. Will PBPD create any new planning or National Environmental Policy Act related requirements?

    No. PBPD procedures complement and enhance the existing planning and NEPA requirements by scoping projects with increased focus on the primary project needs in balance with other agency and community desires, budgetary constraints, and human and environmental impacts. Planning and NEPA requirements ensure that a stakeholder-focused project development process is consistent with the agreed-upon project purpose and need. The process must include evaluation, study, and compliance with the critical steps necessary for approval of federally funded transportation projects and other projects that require Federal approvals. PBPD procedures operate within the existing planning and NEPA requirements.

21. What impact might PBPD have on right-of-way acquisition?

    PBPD does not change the process for acquiring right-of-way (ROW).

22. How does PBPD relate to asset management?

    PBPD provides the flexibility for agencies to make project-level decisions that support asset management priorities. Similar to asset management, PBPD looks at the whole life-cycle cost of an improvement, operates in a financially sustainable manner, and provides a framework to improve performance on a long-term basis. Therefore, a PBPD approach is directly in line with an asset management method of doing business.

23. Will PBPD result in multimodal needs, such as pedestrian and bicyclist needs, being eliminated from projects?

    U.S. Department of Transportation policy is to incorporate safe and convenient walking and bicycling facilities into transportation projects [reference 23 U.S.C. 217 (e)(g)]. States and cities may also have their own Complete Streets policies that indicate how all road user needs should be addressed. Every transportation agency has the responsibility to improve conditions and opportunities for walking and bicycling, and to integrate walking and bicycling into its transportation systems (link to policy statement). Consideration of all users should be included in the development of the project purpose and need. PBPD provides an increased emphasis on the purpose and need as well as the flexibility in developing solutions to meet those needs.

24. Can/should PBPD result in a project that is less safe than the existing condition?

    No project should result in a condition that is less safe than existing conditions. It is conceivable that an agency may face a decision on a design alternative with significant costs and marginal or no contribution to improving safety on a specific project. Making the choice to not pursue that design alternative could provide significant cost savings that, if reinvested in other ways, could lead to overall safety improvement system-wide.

25. What are the challenges of implementing a PBPD process?

    As with implementing any new strategy or process, agencies implementing PBPD may face a variety of challenges and barriers. Agencies may have internal policies and procedures that prohibit the use of certain aspects of PBPD. Agency staff may also be resistant to embracing the PBPD concept of exercising engineering judgment instead of designing to established standards. State departments of transportation that have implemented forms of PBPD have reported that no challenge or barrier was too significant to be overcome with appropriate planning, training, and communication among stakeholders.

    If agencies establish a PBPD approach, challenges will still exist. Agencies must guard against the overemphasis of short-term cost savings at the expense of future corridor and system needs and a marginalization of CSS, complete streets, or other sustainable project development approaches.