Evaluation of Pedestrian and Bicycle Engineering Countermeasures: Rectangular Rapid-Flashing Beacons, HAWKs, Sharrows, Crosswalk Markings, and the Development of an Evaluation Methods Report
CHAPTER 2. IDENTIFICATION OF COUNTERMEASURES
This chapter documents the process used to identify and select the countermeasures that were evaluated in this project.
An extensive literature review of bicycle and pedestrian countermeasure evaluations was conducted. The research team identified published and unpublished reports, papers, and articles that evaluated bicycle and pedestrian countermeasures. From this preliminary list, the team reviewed each source for relevance to the project. References that provided pertinent evaluation information were summarized, and the countermeasure type, number of study sites, experimental design, and study results were noted. The evaluations were also summarized by countermeasure type, indicating the cumulative total number of study sites for each countermeasure. Requests to conduct experimental evaluations of bicycle and pedestrian-related traffic control devices that were not specifically addressed by the 2009 Manual on Uniform Traffic Control Devices (MUTCD) were also summarized.(2)
The following findings were developed based on the information the team gathered:
There have been numerous evaluations of bicycle and pedestrian countermeasures, and
most of these evaluations focused on surrogate safety measures. The literature review identified several reports, papers, and articles documenting the evaluation of engineering countermeasures. Many of these evaluations used behavioral or operational measures of effectiveness (i.e., measures involving pedestrians, bicyclists, and/or motorists) as opposed to actual safety outcomes (i.e., a reduction in pedestrian-vehicle crashes). For example, many studies of pedestrian crossing countermeasures use pedestrian-vehicle conflicts or motorist yielding as a surrogate for a safety outcome. Other examples of surrogate safety measures for bicyclist and pedestrian countermeasures include pedestrian looking behavior, pedestrian compliance with crosswalks and pedestrian signals, motorist braking and other behavior, motorist speed, bicyclist positioning, and bicyclist compliance with traffic control devices.
There may be a direct relationship between the surrogate measure and the safety outcome (i.e., a correlation between conflicts and injury crashes and fatalities) for some surrogate safety measures (e.g., bicyclist-vehicle or pedestrian-vehicle conflicts). With other surrogate safety measures, the relationship is intuitive but not explicit or clearly recognized. For example, advanced stop or yield lines may be effective if a greater percentage of motorists are stopping further away from marked crosswalks to reduce visual screening. However, it has not been demonstrated empirically that having more motorists stop further back from the crosswalk leads to fewer pedestrian-vehicle crashes.
The prevailing use of surrogate safety measures in bicycle and pedestrian countermeasure evaluations reflects the difficulty of using crash reduction as a safety outcome. The following factors make crash data analyses more difficult:
- Exposure data should be collected in the before period; however, this seldom occurs.
- Bicycle and pedestrian crashes occur relatively infrequently and are typically
Therefore, a crash-based evaluation of a pedestrian- or bicycle-related treatment might require hundreds or even thousands of treatment sites (plus an equivalent number of control sites) to have a statistically adequate sample of locations for determining the effectiveness of a treatment on pedestrian or bicycle crashes. Other concerns include the following:
- Regression-to-the-mean effects and site-selection biases, especially for selecting high-crash study sites.
- Significant variations in crash data quality, particularly among local jurisdictions.
- The 1- to 2-year lag in crash reporting following countermeasure installation.
- Difficulty controlling land use or other environmental changes that may affect pedestrian and bicyclist activity levels, behavior, and safety.
Conversely, the following factors make observational studies with surrogate safety measures more appealing:
- Researchers have better control over the data collection process.
- Researchers have experimental control over when the countermeasures are introduced at each site.
- Exposure data can typically be collected in both the before and after periods.
- There is less lag time (typically 1–3 months after installation) in the analysis
- Before and after data are collected in a shorter time period, minimizing possible changes in land use or other environmental variables.
- Researchers have the ability to measure the effects of escalating treatments or varying treatment protocols in a relatively short period of time.
Many countermeasure evaluations have weaknesses in their experimental design or data collection protocol that limit the value of their results. Even a cursory review of the evaluations in the literature review reveals that many studies have not used control sites or alternately introduced and removed the treatment at the same site to adjust for area-wide changes and other potential confounding factors. In addition, researchers have not used sufficient sample sizes in data collection or addressed regression-to-the-mean biases at study sites with high crash rates prior to treatment installation. Many evaluations were conducted by local transportation agencies with limited resources where engineering judgment was typically used when interpreting study results.
Some evaluations treat effectiveness and safety as a binary outcome (i.e., safe or not safe) with little consideration for how it may change for various street characteristics and user populations. For example, the in-street pedestrian crossing sign has been found to be fairly effective on low-speed streets. However, other evaluations of this sign had less than promising results but failed to consider the context in which the sign was measured
(i.e., moderate-speed, high-volume streets). Therefore, it is important for the study design
and the evaluation plan to address the full range of street characteristics. Based on the literature review and evaluation, five candidate bicycle countermeasures and nine candidate pedestrian countermeasures were identified for potential study.
The most promising low-cost bicycle engineering countermeasures that could benefit from additional safety evaluation were as follows (in no particular priority order):
- Shared lane pavement markings: Shared lane pavement markings (a bike symbol with two chevrons) have been tested in San Francisco, CA, and are in the California MUTCD.(3) However, at the time of this review, these markings were not included in the 2003 MUTCD, and numerous cities in other States were using different variations of this pavement marking.(4) Ft. Collins, CO, Minneapolis, MN, and Portland, OR, are evaluating shared lane pavement markings as part of the official experimentation process. The 2009 MUTCD now includes a provision for shared lane markings.(2)
- Colored bike lanes (or other signing and marking) in high-conflict areas: Colored bike lanes are still considered experimental and were not included in the 2003 MUTCD.(4) Several cities have experimented with colored bike lanes, most notably Portland, OR, and Cambridge, MA, while others are currently experimenting with them (i.e., New York City, NY). Some cities have used colored bike lanes only in high-conflict areas, whereas others have proposed to use continuous colored bike lanes.
- Standard width bicycle lanes: Several studies have looked at operational or behavioral effects of standard width bicycle lanes (i.e., approximately 5 ft), but few have quantified the crash experience. Although a sufficient number of study sites could be identified
for crash analysis, gathering exposure data prior to treatment installation could be problematic. Various street characteristics (e.g., on-street parking, driveway/curb cut frequency, etc.) would have to be controlled in a crash analysis.
- Road diet: Road diets are often conversions of four-lane undivided roads into three lanes (two through lanes and a center turn lane/median refuge island), with the fourth lane converted into bicycle lanes, sidewalks, and/or on-street parking. A 2004 FHWA study quantified the crash reduction of road diets for vehicle traffic, but little is known about any potential safety benefits for bicyclists and pedestrians.(5)
- "BICYCLISTS MAY USE FULL LANE" regulatory sign: At the time of this study, the National Committee on Uniform Traffic Control Devices (NCUTCD) was discussing a regulatory sign that would replace the existing "SHARE THE ROAD" sign for bicycles because the sign is ambiguous and can be interpreted differently by bicyclists and motorists. However, it is difficult to quantify the safety effectiveness of similar simple sign treatments even when surrogate safety measures are used.
The most promising low-cost pedestrian engineering countermeasures that could benefit from additional safety evaluation are as follows (in no particular priority order):
- Pedestrian countdown signals: Pedestrian countdown signals have been studied in
San Jose, CA, and most recently in San Francisco, CA. Results of the crash study in
San Francisco, CA, found a significant crash reduction; however, crash reduction was also significant at control sites.(6) The authors indicated that regression-to-the-mean played a major role in the crash decline. Evaluation of pedestrian countdown signals are currently planned as part of FHWA's Intelligent Transportation Systems (ITS) countermeasures study in Miami, FL; Las Vegas, NV; and San Francisco, CA.(7) At this time, there may be a sufficient number of study sites to perform a crash analysis by pooling study sites from several States.
- Median refuge islands: Median refuge islands are often cited as one of the most cost-effective countermeasures; however, many practitioners have indicated a need for additional quantitative data on safety benefits. There are several evaluations of median refuge islands in the literature review, and the FHWA crosswalk marking study by Zegeer et al. indirectly quantified the effects of median refuge islands.(8)
- In-roadway warning lights: In-roadway warning lights have become a popular pedestrian enhancement, and they are found in the 2003 MUTCD.(4) There are several studies that document improved motorist yielding and increased braking distance, particularly in lowlight conditions. However, there has been some discussion about their actual safety benefit, and some engineers have suggested that they be removed from the 2003 MUTCD.(4)
- Rectangular rapid-flashing beacons (RRFBs): The research team has identified a low-cost, solar-powered flashing beacon that includes a strobe display. Preliminary tests in Florida indicate that this beacon may be effective at increasing motorist yielding at uncontrolled crosswalks on multilane, high-volume streets. Since the number of installations is limited, more experimental data are needed.
- Leading pedestrian intervals: Leading pedestrian intervals provide a "head start" for pedestrians before turning traffic is released. There are a few studies that have evaluated leading pedestrian intervals, and it is planned for evaluation in the FHWA ITS countermeasures study in Miami, FL, and San Francisco, CA.(7)
- Raised crosswalks: The literature review contains few studies on raised crosswalks. All studies focused on surrogate safety measures, such as driver yielding. The city of Boulder, CO, has installed numerous raised crosswalks, particularly at right-turn bypass lanes. Raised crosswalks also serve a traffic calming role, but they have limited application on arterial streets.
- Advanced stop or yield line with regulatory sign at marked crosswalks: This countermeasure has been evaluated in several studies and is offered as an option in the 2003 MUTCD, but it is not widely used in practice.(4) Advanced stop or yield lines are thought to be effective at reducing multiple-threat crashes on some roadway types; however, their effectiveness may not be as great for high-speed, high-volume streets.
- Improved crosswalk or intersection lighting: The literature review contains limited evaluations of lighting, with a few studies conducted in the 1970s. The concept of smart lighting, or lighting that becomes brighter in the presence of a pedestrian, is planned for evaluation in the FHWA ITS countermeasures study in Miami, FL, and Las Vegas, NV.(7)
- High intensity Activated crossWalK (HAWK) or pedestrian hybrid signal: The HAWK has been extensively installed in Tucson, AZ; however, a comprehensive safety study has not been performed yet.
A practitioner panel was identified and selected to provide feedback and weighting to the candidate countermeasures. The panel was sent the list of candidate bicycle and pedestrian countermeasures and the following rankings were derived:
- Colored bicycle lanes.
- Shared lane pavement markings.
- Standard width bicycle lanes.
- Advanced stop/yield line.
- Leading pedestrian interval.
- Pedestrian countdown signals.
The next step of the process was to meet with FHWA staff to select the final list of countermeasures for study. Once the countermeasures were selected, the research team would develop an evaluation plan for each countermeasure.
IDENTIFY POTENTIAL EVALUATION SITES AND EXPERIMENTAL DESIGN
After the top bicycle and pedestrian countermeasures were identified, researchers began to search for potential evaluation sites. The experimental designs and measures of effectiveness that would be appropriate for the given countermeasure were also considered. This research team made the following recommendations at a meeting with FHWA staff on October 23, 2006:
Candidate bicycle countermeasure recommendations:
- Colored bike lanes.
- Shared lane pavement markings.
- Standard width bike lanes.
Candidate pedestrian countermeasure recommendations:
- Advance yield/stop lines.
- Countdown signals.
The final consensus on the priority ranking of countermeasures to be evaluated was as follows:
- Shared lane pavement markings for bicyclists.
Following the October 23, 2006, meeting, the research team developed the experimental designs that were used to conduct the evaluation.
Approximately 18 months after evaluations of RRFBs, HAWKs, and shared lane markings for bicyclists began, additional funding was provided to examine a fourth countermeasure and to develop a user-friendly safety evaluation document. The following possibilities were discussed for the fourth countermeasure:
- Driver's view (detection distance) of crosswalk markings.
- Crash rates at midblock crossings.
- Midblock transit stops.
Those in attendance at the meeting determined that the driver's view (detection distance) of crosswalk markings should be the fourth countermeasure for this project. A key question to be explored in the study was whether parallel white lines were sufficient for midblock crosswalks. Additionally, the following components were recognized as necessary for a potential update to the 2003 MUTCD:(4)
- Additional figures or illustrations for crosswalk markings similar to the figures that already exist for school and construction zones.
- Text that indicates differences between intersection and midblock pedestrian crossings.
Participants at the meeting liked the systematic approach of the proposed crosswalk marking study, with one participant expressing the importance of having good basic data.
The development of an evaluation methods report for pedestrian and bicycle traffic control devices was also added as part of the project. The purpose of the report is to teach practicing engineers, planners, and public works employees at the local, county, and State levels how
to conduct an evaluation of traffic control device effectiveness. The need for this report became apparent because many of the evaluations that were reviewed lacked solid experimental design and research methods.