National Academies Press: OpenBook

Traffic Signal Control Strategies for Pedestrians and Bicyclists (2022)

Chapter: Chapter 2 - Understanding User Needs and Establishing Priorities

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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
×
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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
×
Page 7
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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
×
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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
×
Page 9
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Suggested Citation:"Chapter 2 - Understanding User Needs and Establishing Priorities." National Academies of Sciences, Engineering, and Medicine. 2022. Traffic Signal Control Strategies for Pedestrians and Bicyclists. Washington, DC: The National Academies Press. doi: 10.17226/26491.
×
Page 10

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4 In the United States, traffic signal timing is traditionally developed to minimize motor vehicle delay at signalized intersections, with minimal attention paid to the needs of pedes- trians and bicyclists. The unintended consequence is often diminished safety and mobility for pedestrians and bicyclists. The issue is exacerbated when practitioners rely on software tools designed to optimize signal timing by minimizing motor vehicle delay without considering pedestrian delay or safety beyond meeting minimum standards, such as pedestrian clearance time. While not all signal timing implementations follow this process, there are limited tools for practitioners to develop timing plans that incorporate a full understanding of pedestrians’ and bicyclists’ needs. NCHRP Report 812: Signal Timing Manual, 2nd Edition, introduced an outcome-based approach to signal timing, which encourages practitioners to develop signal timing based on a consideration of the operating environment, users, user priorities by movement, and local operational objectives. Within this outcome-based approach, the first step is to identify the types of users present in an environment, understand users’ needs and how they are affected by signal timing and intersection design, and prioritize those needs. 2.1 Identifying and Prioritizing Non-motorized Users As a rule, pedestrians and bicyclists should be considered as intended users of intersections everywhere except where they are prohibited on the intersecting roads. At the same time, the level of priority given to non-motorized user needs should be greater on routes that are used more frequently, are critical for their mobility, or have a safety issue. The following data sources can help determine the degree to which pedestrians and bicyclists should be considered critical users at an intersection: • Bicycle and pedestrian counts: Practitioners should consider collecting bicycle and pedes- trian counts with all intersection turning movement counts. While pedestrian and bicycle counts are not required to implement many of the treatments in this guidebook, quantifying user types and volumes is helpful in designing some treatments, and it is important for deter- mining their priority level in intersection design. Third-party data sources and probe data can be used to supplement traditional counts and, in some cases, can provide a broader perspec- tive than manual counts (e.g., by providing information over longer time periods). • Field visits and observations: Observing the study area can reveal the types of users present at various times of day (peak and off-peak) and days of the week. As part of a field visit, prac- titioners should walk and bike the intersection to gain a better understanding of user experi- ences within and around the study area. Consider road safety audits to conduct a more formal safety performance examination by an independent, multidisciplinary team. C H A P T E R 2 Understanding User Needs and Establishing Priorities

Understanding User Needs and Establishing Priorities 5   • Pedestrian calls/Traffic signal controller data: Pedestrian detections and/or calls at an inter- section can provide insights on the demand profile across the day and by direction. Traffic signal controllers with data-logging capabilities can record the number of times a pedestrian call was placed for intersections using pedestrian pushbuttons. Care must be taken when evaluating this kind of data, however, since pedestrian volumes may or may not be strongly related to pushbutton actuation counts. • Crash history: Practitioners can obtain historical crash data, typically for 3- to 5-year spans, to assess potential safety concerns. The presence of bicycle and pedestrian crashes confirms user activity and may indicate a need for additional treatments to address safety risks. Many agencies utilize crash history as an initial step to identify locations with safety risks and are taking a more proactive, systemic approach to crash reduction. However, crashes alone are not always sufficient to determine user challenges, particularly on low-volume local streets where crash frequencies are low or where safety issues suppress pedestrian or bicyclist demand. • Conflict analysis: Conflicts at signalized intersections are addressed by using dedicated phasing and separating conflicting movements; however, often not all conflicts are eliminated. This includes turning movement conflicts for both left- and right-turning movements. A crash history provides insights into outcomes of these conflicts, but near misses and uncomfort- able pedestrian experiences are not always reported. Identifying and assessing conflicts using analysis is becoming more common, especially as technology advances. Conflict analysis can help practitioners identify potential risks, perhaps before a crash history manifests. Conflicts can be mapped manually or counted using emerging video safety analytic tools. • Land use context: Pedestrian and bicycle service will be more critical where land use sup- ports mobility by foot and by bicycle. For walking, this can include not only traditional downtowns but also suburban locations where origins and destinations are close to one another. Pedestrians should always be expected along transit corridors. Schools and other destinations oriented toward youths or older adults can be important attractors for people on foot and on bike. • Travel patterns: It is important to understand non-motorized users’ likely travel patterns for a variety of trip purposes. Is the intersection part of a local or regional bicycle network plan? If not, is it the only nearby direct route that cyclists can follow? Is there a trail or multiuse path nearby? Is it a pedestrian or bicycle access route to shopping, employment, or recreation destinations? At every transit stop, pedestrian crossing demand can be assumed. • Demographics: Census data can assist in identifying areas with likely pedestrian or bicyclist demand or special user needs (e.g., areas with a concentration of older or low-income resi- dents or households without access to automobiles). For example, children and older adults may have slower walking speeds and need more time to cross the street. Similarly, in com- munities with a high number of persons with disabilities or visual impairments, accessible routes should be prioritized. • Community insights: Agencies may become aware of non-motorized user needs through public involvement activities and customer requests. Other sources on the list can help agen- cies evaluate these requests and concerns. 2.2 Pedestrian and Bicyclist Needs Pedestrians and bicyclists have the same basic needs as intersection users in motor vehicles: maximizing safety and minimizing delay. They also have basic needs stemming from their vul- nerability and reliance on human power. Additionally, walking is a mode of transportation that is more easily accessible to persons with vision impairments or other disabilities, so intersections must meet pedestrian accessibility needs lest they become barriers to mobility.

6 Traffic Signal Control Strategies for Pedestrians and Bicyclists Pedestrian and cyclist needs that should be addressed in the design of traffic signal timing plans and traffic signal equipment can be grouped into the following four categories: • Safety and comfort • Minimizing delay • Ease of use and information • Accessibility 2.2.1 Safety and Comfort Pedestrians and cyclists should be able to cross intersections with little risk of crash or injury. With motor traffic, safety is often measured in terms of crashes because motor vehicle volumes are typically so great that any underlying safety risk will readily be manifested in crash statistics. Because of the lower relative volume of pedestrians and bicycles on our streets, having a small number of crashes is not sufficient to prove that risk is low. Some agencies have adopted a systemic safety approach, recognizing that even in the absence of recorded crashes at a particular location, there may still be an underlying safety problem. This can be revealed either through a systematic analysis of injury data over a wide range of similar situations or through an understanding of pertinent human limitations regarding vulnerability and ability to see, judge, and make correct decisions (Furth & Wagenbuur, 2017). For example, an intersection may have no record of bicycle crashes with left-turning vehicles, but if it fits the profile of an intersection type known to have this kind of crash, the risk should be recognized and measures should be taken to reduce it. Comfort in the context of non-motorized users means perceived safety, which can often go beyond objective safety. For example, if pedestrians need 30 seconds (s) to cross the street and the traffic signal holds conflicting traffic for 30 s, it could be said that they are technically safe. However, if signals are timed so that the pedestrian display goes to steady Don’t Walk and the countdown timer goes blank when pedestrians still have two lanes to cross, they may fear being caught in the road when conflicting traffic starts to move. Intersections should be designed so that pedestrians and bicycles can cross in both safety and comfort. Comfort also means an absence of “uncomfortable” interactions with motor vehicles. Cross- ings often involve permitted conflicts in which turning vehicles are allowed to run at the same time as crossing pedestrians and bicycles. Rules of the road indicate that those turning motorists are supposed to yield the right-of-way. But where intersection geometry allows for high-speed turns or where turning traffic volume is high, turning motorists may be less likely to yield; this creates an asymmetric and uncomfortable challenge over who is going to stop for whom. There are several treatments in Chapter 6 of this guidebook to reduce or eliminate this kind of interaction. 2.2.2 Minimizing Delay Just like motorists, pedestrians and bicyclists value their time and therefore want to minimize delay. Waiting can be even more onerous for pedestrians and bicyclists compared to motorists because they are exposed to the weather. And importantly, it is well-known that pedestrian and bicyclist compliance with signals diminishes when they have to wait a long time; that makes pedestrian and cyclist delay a matter not only of convenience but also of safety. While intersection and signal timing design in the U.S. is strongly oriented around mini- mizing delay for vehicles, methods for pedestrian timing typically focus only on meeting safety standards (such as providing sufficient clearance time). Little or no attention is paid to

Understanding User Needs and Establishing Priorities 7   minimizing pedestrian delay. The current framework of traffic signal timing design needs to be changed to one that aims to minimize pedestrian and bicycle delays as well as motor vehicle delay. Chapter 7 and Chapter 10 describe several treatments that can be used to reduce pedes- trian delay, while Chapter 9 describes several treatments that can lower bicycle delay. Examples provided in those sections show that in many situations, pedestrian and/or bicycle delay can be dramatically reduced by timing plan adjustments that have little or no impact on vehicle delay. Perhaps the greatest reason for the lack of pedestrian-friendly signal timing plans is that neither pedestrian delay nor bicycle delay is usually measured or reported at all, while vehicular delay has been the key performance measure in intersection evaluation. Software typically used for traffic signal timing does not calculate pedestrian or bicycle delay. The business maxim that “only what’s measured counts” has proven true. Agencies wishing to improve service for pedestrians and bicycles at traffic signals can con- sider establishing a policy that requires intersection analyses reporting vehicular delay to also report pedestrian and bicycle delays, along with a level of service (LOS) rating that allows a direct comparison with vehicular LOS where used. Such a policy should apply to intersec- tion analyses that agencies perform themselves as well as to those submitted to an agency for approval, such as developer-initiated traffic impact studies. It should require reporting average pedestrian and bicycle delays by crossing and by direction for multistage crossings because a long delay for any crossing movement can indicate a safety issue. A commonly used scale for determining LOS, based on pedestrian delay from TRB’s fourth edition of Highway Capacity Manual (HCM 2000), is reproduced below as Exhibit 2-1. No standard scale for the delay-based LOS of bicycles has been established, but the same scale used for pedestrians may be appro- priate because bicyclists also are exposed to weather and exhibit significant noncompliance when waiting times are long. 2.2.3 Improving Ease of Use and Information Pedestrians and bicyclists want the crossing experience to be easy, and they want to receive information on how the system is going to serve them, which reduces anxiety. Being detected should not require searching for a pushbutton or going out of one’s way. Just as people using an elevator appreciate the confirmation light that illuminates when they push a button, so do pedestrians and bicyclists want to see confirmation that they have been detected. Countdown displays assure pedestrians as they cross that they will have enough time to finish and help faster pedestrians decide, based on their own walking speed, whether it is safe to begin crossing. Chapter 8 describes treatments related to added information and convenience. Consider requiring that pedestrian delay be reported as part of intersection analysis. For example, Cambridge, MA, has long required that consultants preparing traffic impact analyses for city approval report pedestrian delay and its corresponding LOS along with vehicle delay. In the Netherlands, it has long been standard practice for pedestrian and bicycle delay to be reported in any intersection analysis along with vehicle delay. Source: HCM 2000, Exhibit 18–9. Level of Service Average Pedestrian Delay (s) Likelihood of Noncompliance A < 10 Low B > 10–20 C > 20–30 Moderate D > 30–40 E > 40–60 High F > 60 Very high Exhibit 2-1. LOS for pedestrian delay at signalized intersections.

8 Traffic Signal Control Strategies for Pedestrians and Bicyclists 2.2.4 Accessibility Intersection crossings should be accessible to all pedestrians, including those with disabilities. Persons with vision impairments especially rely on walking and transit for their mobility because they may have additional challenges operating motor vehicles or riding a bicycle. Therefore, it is vital that intersection crossings be accessible to them, not only in a legal sense but also function- ally. While many pedestrians with vision disabilities use audible traffic cues—for example, the initial surge of traffic departing when a signal turns green is a cue to begin crossing—the inter- section design should ensure that audible cues are provided. In general, accessible pedestrian signals (APS) are needed wherever visual pedestrian signals are installed to positively convey the status of the signal to individuals with vision disabilities so they are not delayed in starting to cross the street. When the time programmed for pedestrians to start crossing is different from the time when traffic gets a green light, such as in the leading pedestrian interval, APS are particularly needed to let pedestrians with vision disabilities know that the Walk interval is not concurrent with traffic and to cue all pedestrians to the non-concurrent signal timing. Pushbutton detectors and APS should be located far enough apart from each other, yet in line with their respective crosswalk, that a person relying on a pushbutton locator tone can find the pushbutton for the right crosswalk and can distinguish which APS device is providing the Walk indication. Many older adults, young children, and persons with walking impairments can only walk at a limited speed. Signalized crossings should make it feasible for the vast majority of the population to cross the street; without them, wide streets become impassable barriers for people on foot. A lack of signalized crossings can make not only walking but also transit infeasible as a mode of transportation, as it generally requires crossing the street either when coming or going. Tradi- tionally, the need to accommodate slower crossers has been “met” by having engineers calculate a clearance time based on a (slower-than-average) pedestrian design speed. This guidebook urges practitioners to go beyond meeting minimum standards by optimizing accessibility for slower pedestrians. For example, consider evaluating signal timing plans by a performance mea- sure that indicates the lowest pedestrian speed that will be supported in signal timing strategies. Accessibility considerations are incorporated throughout this guidebook and are addressed as part of the description of every treatment in the toolbox. 2.3 Establishing Objectives and Priorities The primary objective of traffic signal control is to meet user needs. To have practical force, user needs should be enumerated and expressed in terms of specific objectives for the agency— for example, to minimize pedestrian and bicycle collisions as well as auto collisions; to maximize pedestrians’ and bicyclists’ sense of security; to minimize pedestrian and bicycle delays as well as vehicle delay; to be an industry leader in providing information to pedestrians and bicyclists; and to make crossings accessible to as many people as possible. For each objective, agencies can specify one or more performance measures, such as fre- quency of conflicts, average delay, and lowest pedestrian speed. Target values or standards for those measures should guide design and provide a means for evaluating current unmet needs as well as the success of a treatment. Objectives for signalized intersection design will sometimes conflict with each other or at least involve a trade-off. For example, improving pedestrian and bicycle safety might involve treatments that increase vehicle delay, or a treatment that would benefit pedestrians or bicycles might involve new equipment costs. Therefore, an agency’s review of user needs extends to deciding how much priority to assign to the various user needs. Greater priority to pedestrian or bicycle safety can mean, among other things, willingness to accept a greater increase in vehicle

Understanding User Needs and Establishing Priorities 9   delay or equipment cost. Greater priority can also be reflected in the use of a stricter target or standard for a performance measure, such as a lower pedestrian design speed or a stricter limit on average pedestrian delay. Priorities are also an important input for project programming (i.e., determining which projects should be done first). Possible reasons to assign greater priority to pedestrians and bicycles than motorized users include a large number of pedestrians or bicycles, regular use by pedestrians with disabilities or low walking speeds, being part of a critical route in the bicycle network, a history of injuries to pedestrians and bicyclists, and broader transportation policies calling for improved safety for vulnerable road users and/or promoting walking and bicycling. At the same time, there can be reasons to assign priority to other modes, such as high vehicular volume or the presence of a high-frequency bus route. In Amsterdam, Netherlands, planners have designated a priority net- work each for autos, bicycles, and transit, with the restriction that no road segment may belong to more than two priority networks; these network plans are important inputs in assigning priorities in intersection design. Assigning a low priority to pedestrian or bicycle needs does not necessarily entail only meeting minimum standards on their behalf. Many of the treatments described in this guidebook offer substantial improvements in service and/or safety to pedestrians and bicycles with little or no detriment to vehicle capacity or delay, and many treatments can be applied with little or no cost. Even where pedestrians and bicycles are not high-priority users, signal control design should still aim to maximize their safety, minimize their delay, and maximize their convenience and accessibility. 2.4 Understanding Agency Capabilities Agency funding, maintenance and staff demands, equipment constraints, and established policies regarding signal operations can play a role in determining whether certain treatments can be applied. Maintenance and Staff Support. Some of the treatments described in the toolbox may require added maintenance efforts or ongoing operational support. Treatments that are experi- mental or have only interim approval may require staff effort or additional support in order to apply to FHWA for permission to experiment. For each treatment described in the toolbox, Considerations and Implementation Support sections provide pertinent information on its likely maintenance and staff support demands. Costs and Constraints for Equipment and Software. Many of the treatments described in the toolbox require additional equipment, such as new signal heads. While most of the treat- ments can be supported with standard signal control equipment and software, some may require upgraded or specialized equipment/software or specialized programming with existing software. With each treatment, the toolbox provides pertinent information regarding controller capabili- ties, possible software needs, and possible new equipment needs. Agency Policy. Many transportation agencies have established policies related to signal operation (e.g., length of Walk interval, upper and lower limits for cycle length) and mobility and safety performance targets that can support the resulting policies. Ideally, an agency’s poli- cies will support the implementation of a preferred treatment. However, where there is a conflict (e.g., an agency policy that does not allow flashing operation), practitioners may need to consider whether or how that conflict can be resolved. FHWA provides additional resources for agencies wishing to gain a better understanding of their current capabilities and the effect of their capabilities on traffic management.

10 Traffic Signal Control Strategies for Pedestrians and Bicyclists Bibliography FHWA. (2021, March 1). Welcome to Business Process Frameworks for Transportation Operations. Retrieved July 1, 2020, from https://ops.fhwa.dot.gov/tsmoframeworktool/index.htm Furth, P. G., & Wagenbuur, M. (2017). Systematic Safety: The Principles behind Vision Zero [Video]. YouTube. https://www.youtube.com/watch?v=5aNtsWvNYKE Highway Capacity Manual. (2000). TRB, National Research Council, Washington, DC. Urbanik, T., Tanaka, A., Lozner, B., Lindstrom, E., Lee, K., Quayle, S., Beaird, S., Tsoi, S., Ryus, P., Gettman, D., Sunkari, S., Balke, K., & Bullock, D. (2015). NCHRP Report 812: Signal Timing Manual, 2nd Edition. Trans- portation Research Board, Washington, DC.

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In the United States, traffic signal timing is traditionally developed to minimize motor vehicle delay at signalized intersections, with minimal attention paid to the needs of pedestrians and bicyclists. The unintended consequence is often diminished safety and mobility for pedestrians and bicyclists.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 969: Traffic Signal Control Strategies for Pedestrians and Bicyclists is a guidebook that provides tools, performance measures, and policy information to help agencies design and operate signalized intersections in a way that improves safety and service for pedestrians and bicyclists while still meeting the needs of motorized road users.

Supplemental to the report are presentations of preliminary findings, strategies, and summary overview.

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