CHAPTER 5

Summary of Findings

The objective of the synthesis was to review and document state DOT practices regarding the implementation of the FHWA PSCs. The synthesis scope included: FHWA PSCs piloted, implemented, or adopted as policy or procedures by DOTs; the extent, scale, and frequency to which each countermeasure has been implemented; factors affecting different implementation approaches within a given state; DOTs’ evaluation of the FHWA PSCs after implementation; barriers to the implementation of the FHWA PSCs and DOTs’ modifications and strategies to overcome those barriers; and future research needs.

Methods used to achieve the synthesis objectives included a literature review, survey, and follow-up interviews. Various sources such as guides, evaluation studies, websites, DOT policies and standards, and other resources were reviewed and compiled. An online survey questionnaire was distributed to all 50 state DOTs and the District of Columbia DOT. Survey responses were received from 49 DOTs, for a response rate of 96%. Case examples for six DOTs (California, Minnesota, Nebraska, Nevada, Ohio, and Vermont) were developed through follow-up interviews. In consultation with the topic panel, criteria considered as a basis for choosing the DOTs for the case examples included

• Diversity concerning geography, level of experience, number and type of FHWA PSCs implemented, stages of implementation, customizations, and implementation challenges;
• Some preference for states with topic panel members; and
• Willingness to participate in a case example, as indicated in the survey (24 DOTs).

Summary of Key Findings by Topic

Key findings from the synthesis based on the literature review, survey results, and follow-up interviews are described in the following sections, which are organized by topic.

Resources for FHWA PSCs

• FHWA provides a webpage with information about the 28 PSCs, organized into five categories (FHWA 2024a). FHWA webpages for individual PSCs provide information such as a general overview of the PSC, safety benefits, and related links.
• FHWA’s PSC resources are often consulted by DOTs during the development of safety projects.
• General information on FHWA PSCs is also available from various DOTs, such as Caltrans (2024a) and Florida DOT (2022).
• Many of the emphasis areas described by DOTs in their SHSP reports correspond to FHWA PSCs. DOTs often include pedestrians and bicyclists as an emphasis area, while other emphasis areas related to the FHWA PSCs include speeding, roadway departure crashes, and intersections.

• DOTs describe various safety-related programs and provide project lists in their HSIP report. Examples of programs related to FHWA PSCs include horizontal curves, intersections, median barriers, pedestrian safety, roadway departure, sign replacement and improvement, lighting, local safety, SafetyEdge, and HFST. Example projects related to FHWA PSCs include installing sidewalks, roundabout construction or modifications, shoulder widening, continuous roadway lighting, adding/modifying auxiliary lanes, HFST, rumble strips, cable barriers, road diets, LRSPs, RSAs, and shared use paths.
• Twenty-eight responding DOTs have developed policies, processes, procedures, or tools that consider and prioritize FHWA PSCs for implementation.
• Regarding PSC-specific resources for PSCs categorized as Assessment Stage or Institutionalized by each DOT, responding DOTs have most frequently developed policies, standards, guidelines, or training materials for the following FHWA PSCs: implementation of longitudinal rumble strips and stripes on two-lane roads, SafetyEdge, and median barriers. SSCs and VSLs are the PSCs least frequently noted by responding DOTs as having resources developed.
• Examples of types of resources developed by DOTs for FHWA PSCs include guidelines, standard drawings, implementation policies, selection charts or decision matrices, concept of operations, report templates, and public outreach materials.
• Responding DOTs have most frequently conducted evaluation studies for the following FHWA PSCs: roundabouts, longitudinal rumble strips and stripes on two-lane roads, road diets, median barriers, and pavement friction management.
• As noted in the survey responses, no responding DOTs have completed evaluation studies for LPI, walkways, and LRSPs. One responding DOT has completed evaluation studies for each of the following PSCs: SafetyEdge, backplates with retroreflective borders, dedicated left- and right-turn lanes at intersections, and systemic application of multiple low-cost countermeasures at stop-controlled intersections.

DOT Extent of Use of FHWA PSCs

• All 49 of the DOTs that responded to the survey use FHWA PSCs to some extent.
• DOTs implement a wide range of FHWA PSCs to various degrees. The FHWA PSCs that are most frequently Institutionalized by responding DOTs are longitudinal rumble strips and stripes on two-lane roads, median barriers, enhanced delineation for horizontal curves, and roundabouts. The number of Institutionalized FHWA PSCs per responding DOT varies from one to 27.
• The most prevalent FHWA PSCs for the other implementation stages are
  • Not Implemented: SSCs and VSLs,
  • Development Stage: appropriate speed limits for all users and reduced left-turn conflict intersections,
  • Demonstration Stage: LPI and corridor access management, and
  • Assessment Stage: systemic application of multiple low-cost countermeasures at stop-controlled intersections and medians and pedestrian refuge islands in urban and suburban areas.
• As indicated by the average stage index, overall implementation levels are the highest for longitudinal rumble strips and stripes on two-lane roads, roundabouts, and dedicated left- and right-turn lanes at intersections and lowest for appropriate speed limits for all road users, VSLs, and SSCs.
• Responding DOTs deploy an average 13.5 of FHWA PSCs as standard practice. The FHWA PSCs that are most frequently implemented as standard practice by responding DOTs are longitudinal rumble strips and stripes on two-lane roads, backplates with retroreflective borders, yellow change intervals, and SafetyEdge.

• The most frequently considered FHWA PSCs that are Institutionalized (but not standard practice for a given responding DOT) for use on projects are enhanced delineation for horizontal curves, roundabouts, and crosswalk visibility enhancements.

DOT Practices for Implementation of FHWA PSCs

• Approaches used to implement FHWA PSCs include assessing cost effectiveness and achieving the highest reductions in crash fatalities and serious injuries, selecting treatment types instead of specific locations or specific projects, and analyses performed at a project-by-project specific level using HSIP application scoring criteria.
• Various funding mechanisms for FHWA PSCs are used, and the funding source sometimes varies based on the implementation stage of the PSC. Funding sources include HSIP funds, state funds (pilot projects), maintenance funds, and project funds (FHWA PSCs that are standard practice).
• Example practices used to assess the safety performance of FHWA PSCs include before-and-after studies, an ongoing contract in place to assess various traffic safety countermeasures, and informal observational data.
• Pilot projects are sometimes used when first implementing an FHWA PSC to evaluate its effectiveness and to assess state-specific implementation considerations such as public perception and design criteria.
• Approaches to implementation of FHWA PSCs differ based on different regions or areas of the state for 21 responding DOTs. All 21 of these DOTs noted context or area type as a factor influencing their implementation of FHWA PSCs in different areas or regions of the state, while most of them also indicated that land use and safety performance are influential factors.
• State DOT partnerships with local agencies in implementing FHWA PSCs are pursued in various ways, such as providing them with resources, including them as stakeholders, assisting with LRSP development, promoting them through LTAP, and providing funding for local safety projects.

DOT Challenges to Implementing FHWA PSCs

• Some of the general challenges faced by DOTs in the implementation of FHWA PSCs include staffing or funding constraints, getting buy-in to the safety research, pushback from internal staff and local agencies, outreach and education, public perception (especially for newer concepts such as reduced left-turn conflict intersections, bike lanes, and road diets), finding pilot projects, shifting to a proactive approach to safety, maintenance concerns, regulatory barriers, funding needs, the need for complementary PSCs to improve safety performance, and the lack of crash data on tribal lands.
• DOTs perceive a wide range of factors as challenges to the implementation of the FHWA PSCs related to speed management. In general, implementation concerns are perceived by responding DOTs as the greatest challenge to the use of FHWA PSCs. SSCs, VSLs, and appropriate speed limits for all road users were cited most frequently by responding DOTs for having factors that hinder efforts to implement FHWA PSCs, while longitudinal rumble strips and stripes on two-lane roads and roundabouts were cited least frequently.
• Examples of challenges to the use of specific FHWA PSCs include
  • SSCs and VSLs: implementation concerns and regulatory barriers (e.g., speed limits for VSLs being only advisory);
  • PHBs: lack of public acceptance and understanding;
  • Pavement friction management: experience with delamination and need for additional information on safety benefits;

• • Wider edge lines: paint shortages that led to higher costs for wider edge lines and inventory and tracking issues;
  • Longitudinal rumble strips and stripes on two-lane roads: need for proper installation equipment;
  • Backplates with retroreflective borders: not realizing safety benefits (possibly due to standardization of signal equipment and features);
  • Rectangular rapid flashing beacons (RRFBs), enhanced delineation for horizontal curves, systemic application of multiple low-cost countermeasures at stop-controlled intersections, and SSCs: performance of solar-powered traffic control devices in cloudy weather;
  • Lighting: existing right-of-way constraints (e.g., sidewalks, utility poles); and
  • RSAs: implementing findings.
• Twenty-nine responding DOTs indicated that they have not stopped using any FHWA PSCs. The following FHWA PSCs are no longer utilized by at least one responding DOT: appropriate speed limits for all users, SSCs, VSLs, PHBs, SafetyEdge, backplates with retroreflective borders, and pavement friction management. Responding DOTs noted stakeholder concerns as a factor in their decision to stop using each of these seven FHWA PSCs except for SafetyEdge. Other reasons cited include
  • Appropriate speed limits for all users: results similar to current DOT process;
  • SSCs: the need for legislation;
  • VSLs: increased emphasis on other SCs or initiatives, cost to implement;
  • PHBs: potential for driver confusion;
  • SafetyEdge: lack of adequate pavement thickness, cost to implement;
  • Backplates with retroreflective borders: increased emphasis on other SCs or initiatives, cost to implement, need for more research regarding safety outcomes; and
  • Pavement friction treatment: cost to implement, delamination issues, and adverse effects on the pavement life cycle.

DOT Modifications or Alternative Strategies for FHWA PSCs

• DOTs pursue various types of modifications or alternative strategies when implementing FHWA PSCs and/or overcoming barriers to implementation. The FHWA PSCs with the highest number of responding DOTs that have implemented modifications or alternative strategies are roundabouts and road diets. The most prevalent FHWA PSCs for each type of modification or alternative strategy are
  • Physical Changes: roundabouts;
  • Change in Approach or Method to Implement: appropriate speed limits for all road users, bicycle lanes, and backplates with retroreflective borders;
  • Alternative Delivery Mechanisms or Funding Sources: systemic application of multiple low-cost countermeasures at stop-controlled intersections, enhanced delineation for horizontal curves, and backplates with retroreflective borders;
  • Pilot Projects: RRFBs, SSCs, VSLs, and road diets;
  • Change in Approach to Public Outreach: roundabouts, reduced left-turn conflict intersections, corridor access management, and road diets; and
  • None: yellow change intervals, RSAs, and dedicated left- and right-turn lanes at intersections.
• Different strategies are used to overcome implementation challenges for FHWA PSCs, such as including maintenance personnel as stakeholders, enhancing public involvement efforts to get more engagement from stakeholders in the decision-making process, providing outreach and training, and being selective in the use of FHWA PSCs to help ensure success and avoid implementation challenges that could hinder future efforts.
• Example modifications or alternative strategies to specific FHWA PSCs include revising standards for rumble strips and SafetyEdge, limiting the installation of rumble strips to new

• pavement, developing installation specifications for rumble strips, increasing the gap for centerline rumble strips to avoid pavement joints, including gaps in rumble strips to accommodate bicyclists, modular roundabouts, sinusoidal rumble strips to address noise concerns, and bundling multiple locations for lighting improvements.

Opportunities for FHWA PSCs

• Examples of ways DOTs are working toward enhancing their use of FHWA PSCs in the future include developing state-specific CMFs, creating guidance for all 28 FHWA PSCs in one document, updating guidance for corridor access management to make it more prescriptive, providing local agencies with additional guidance on implementation, incorporating FHWA PSCs earlier in the project development process, implementing risk-based analyses, augmenting methods for regular assessment, finding ways to utilize pilot projects, increasing the use of PSCs at intersections, developing a pedestrian level lighting standard, expanding use of LPIs and developing guidelines for their use, and conducting a pilot study for a target speed program.
• DOTs are interested in learning about various aspects of other state DOTs’ experiences with FHWA PSCs, such as successes, challenges, strategies used to overcome those challenges, processes used to implement PSCs as standard practice, maintenance practices, use of other PSCs beyond the standard 28 PSCs, supporting local agencies, implementation of RSA findings, deployment of reduced left-turn conflict intersections, and practices for road diets.
• Opportunities suggested by these DOTs to enhance FHWA’s PSC initiative include providing additional information on average benefit-cost ratios for PSCs to help DOTs prioritize them based on level of impact, posting tables or data for all PSCs regarding CMFs and crash severity that are easily distinguishable and comparable for each PSC, adding information on conditions that may not be suitable for the use of specific PSCs, creating short informational videos on PSCs, and developing additional guidance for design and implementation of FHWA PSCs (including actionable steps).

Summary of Key Findings by FHWA PSC

A summary of key findings by FHWA PSC is provided in Table 16. The second and third columns in the table are shaded based on a color gradient corresponding to the values in those columns, where green indicates a high number and red indicates a low number.

Suggestions for Future Research

This synthesis has identified some gaps in existing knowledge and future research needs to enhance practices for the use of FHWA PSCs in the United States. Suggestions for future research include the following:

• Additional research studies to evaluate the safety performance of FHWA PSCs, especially for those PSCs with a limited number of existing evaluation studies or outdated evaluation studies (e.g., LPI, walkways, roadside design improvements at curves, lighting, and LRSPs).
• Development of a guidebook to provide direction and actionable steps for the implementation of FHWA PSCs. Potential topics for the guidebook could include implementation guidance, maintenance considerations, public outreach, funding, modifications or alternative strategies, and case studies.
• The development of additional tools and resources (e.g., benefit-cost assessment tools, maintenance guidance, technical assistance) to help support PSC implementation.

• The creation of outreach materials for FHWA PSCs, especially those that incorporate newer concepts and may potentially encounter resistance from stakeholders (e.g., reduced left-turn conflict intersections).
• The development of enhanced guidance for FHWA PSCs related to speed management (appropriate speed limits for all users, SSCs, and VSLs) that provides strategies on how to overcome challenges such as regulatory barriers.
• The implementation of a clearinghouse that includes DOT and FHWA resources, evaluations, tables or data for all PSCs regarding CMFs and crash severity to facilitate comparisons, information on conditions that may not be suitable for the use of specific PSCs, short informational videos on PSCs, and examples of modifications or alternative strategies for FHWA PSCs to facilitate the sharing of knowledge among DOTs, metropolitan planning agencies, and local agencies.

Table 16. Summary of key synthesis findings by FHWA PSC.

^* Calculated based on these values from survey responses: 0 = Not Implemented, 1 = Development Stage, 2 = Demonstration Stage, 3 = Assessment Stage, 4 = Institutionalized.

NOTE: Avg. = Average, No. = Number, Implement. = Implementation. Sort order = Average Stage Index (high to low).