National Academies Press: OpenBook

Improving Pedestrian Safety at Unsignalized Crossings (2006)

Chapter: Chapter 4 - Review of Pedestrian Signal Warrant

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Suggested Citation:"Chapter 4 - Review of Pedestrian Signal Warrant." National Academies of Sciences, Engineering, and Medicine. 2006. Improving Pedestrian Safety at Unsignalized Crossings. Washington, DC: The National Academies Press. doi: 10.17226/13962.
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Suggested Citation:"Chapter 4 - Review of Pedestrian Signal Warrant." National Academies of Sciences, Engineering, and Medicine. 2006. Improving Pedestrian Safety at Unsignalized Crossings. Washington, DC: The National Academies Press. doi: 10.17226/13962.
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Suggested Citation:"Chapter 4 - Review of Pedestrian Signal Warrant." National Academies of Sciences, Engineering, and Medicine. 2006. Improving Pedestrian Safety at Unsignalized Crossings. Washington, DC: The National Academies Press. doi: 10.17226/13962.
×
Page 24
Page 25
Suggested Citation:"Chapter 4 - Review of Pedestrian Signal Warrant." National Academies of Sciences, Engineering, and Medicine. 2006. Improving Pedestrian Safety at Unsignalized Crossings. Washington, DC: The National Academies Press. doi: 10.17226/13962.
×
Page 25
Page 26
Suggested Citation:"Chapter 4 - Review of Pedestrian Signal Warrant." National Academies of Sciences, Engineering, and Medicine. 2006. Improving Pedestrian Safety at Unsignalized Crossings. Washington, DC: The National Academies Press. doi: 10.17226/13962.
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Page 26

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22 This chapter summarizes the research team’s review and critique of the existing MUTCD pedestrian traffic signal war- rant. Details on reviews conducted on the pedestrian signal warrant are included in the following appendixes: • Appendix G summarizes international signal warranting practices. • Appendix H summarizes the basis for and use of the MUTCD pedestrian signal warrant. • A workshop was held to explore the use of engineering judg- ment in evaluating intersections to determine if a signal should be considered. The details of the workshop efforts are documented in Appendix I. The recommendations for changes to the pedestrian signal warrant submitted to the National Committee on Uniform Traffic Control Devices in June 2005 and January 2006 are in Appendix B. The development of those recommendations, along with the pedestrian treatment guidelines (which use the signal warrant criteria as part of the guidelines) is discussed in Appendix O. A summary of the critique of the MUTCD pedestrian signal warrant follows. Review of Current Pedestrian Signal Warrant The current MUTCD pedestrian signal warrant (War- rant 4) has many factors to be considered when evaluating whether or not a signal is warranted. For this TCRP/NCHRP project, these factors were split into three levels: primary factors, secondary factors, and not related to current research study. These levels reflect the type of requirement as indicated in the language of the MUTCD and the rele- vance to the issue being studied. Primary factors must be considered and include available vehicular gaps (based on critical gap), pedestrian volume, and distance to the nearest traffic signal. A secondary factor is walking speed, which is used to adjust pedestrian volumes. Despite the wide range of factors included in the current pedestrian signal warrant, other factors could be considered. For example, a correlation between acceptable gap criteria and factors such as pedestrian age, pedestrian vision (and walking) abilities, vehicle speed, and roadway cross section is reasonable. Also, the warrant does not mention safety considerations. Par- ticularly critical to this project, there is no consideration of pedestrian generators, such as transit stops, within the war- ranting criteria. There are also no allowances for pedestrian volumes that could result from the installation of pedestrian- friendly treatments. Pedestrian delay is the measure used in the HCM (23) to determine the level of service for pedestrians. Delay is not directly considered in the signal warrant; however, it relates to other variables such as pedestrian volume and gaps. Other attributes of the warrant could be a reference to alternative means of traffic control and how to determine the size of the adequate gap length. The guidance section of the MUTCD could be expanded to note that if a signal is not war- ranted, then less restrictive controls may be appropriate, for example, in-roadway warning lights. Information on how to calculate critical gaps could provide the user with the pre- ferred method for determining the value. The Highway Capacity Manual has a method to calculate critical gap for a single pedestrian or a group critical gap in Chapter 18 and could be referenced (23). The following summarizes the key factors introduced above. Additional details are provided in Appendix H. Primary and Secondary Factors Primary and secondary factors include the following: • Vehicular Gap. The gap criterion was introduced in 1988. The criterion was derived from ITE’s school crossing guidelines (dating back to 1962). The guidelines were based C H A P T E R 4 Review of Pedestrian Signal Warrant

on an old but common traffic signal timing scheme of fixed 60-s cycles. It is very difficult to maintain 60-s cycle lengths because of pedestrian phasing and left-turn phasing. • Pedestrian Volume. The current pedestrian volumes are higher than most of the previous research recommenda- tions, which were developed based on different factors. Comparing the pedestrian volumes included in Warrant 4 with the vehicular volumes in other warrants reveals some interesting trends. Warrant 2 considers minor road traffic volume for 4 hours, while Warrant 3 considers minor road traffic volume for the peak hour. Warrant 4, which uses pedestrian values, also includes peak hour and 4-hour cri- teria. A difference is that only one “minor approach” value is provided in Warrant 4 rather than the sliding scale pres- ent in Warrants 2 and 3. In other words, as the major street volume increases in Warrants 2 and 3, the needed minor street volume to warrant a signal decreases. For the pedes- trian warrant, a single “minor approach” value is provided. A second difference is that the vehicle warrants include a reduction factor for population and major roadway speed while the pedestrian warrant does not. Another difference is the minimum number of vehicles or pedestrians needed to warrant a signal. A comparison of the lower threshold volumes is shown in Table 10. For example, an intersection with only 100 vehicles for the peak hour would warrant a signal before a midblock location with 143 pedestrians per hour. When the 70 percent factor is used, the differ- ence becomes even more pronounced. An intersection could warrant a signal with only 75 vehicles while 143 pedestrians would still be required. This comparison assumes a high number of vehicles on the major road; however, it does demonstrate a difference between vehicles and pedestrians. • Distance to Nearest Traffic Signal. The current warrant includes a provision that a signal shall not be considered at locations within 300 ft (91 m) of another signal. This is believed to be based on the distance a pedestrian will walk in order to cross the major street. The researchers did not identify data that support this distance or other distances of how far beyond the desired path a pedestrian would be willing to walk. The U.S. DOT’s 1995 Nationwide Personal Transportation Survey did find that most pedestrian trips (73 percent) are 0.5 mi (0.8 km) or less (3). With most trips being about 2,600 ft (792 m), pedestrians might not be willing to increase their trip length by more than 10 per- cent in order to walk to a different crossing location. As part of the on-street pedestrian surveys documented in Appendix K, those interviewed were asked “if this crossing was not here, would you walk to the next intersection (point to intersection of interest)?”For three of the sites, only about 25 percent of the respondents would walk to a sig- nalized intersection at 550, 950, or 1,000 ft (168, 290, or 305 m). For the site with a signalized intersection about 200 ft (61 m) from the crossing, about 50 percent of those interviewed would walk to that crossing. The remaining site where this question was appropriate did not follow similar findings. A much higher percentage indicated that they would be willing to walk to another crossing. Over 65 percent of the respondents indicated that they would walk 600 ft (183 m) to cross at a signalized crossing. The greater 23 Lower Threshold Volume (Pedestrian or Vehicle on Highest Volume Minor Road Approach) Peak Hour Four Hour Condition Number of Lanes on Minor Road Approach Warrant 3 b Vehicular (vph) Warrant 4 c Pedestrian (ped/h) Warrant 2 d Vehicular (vph) Warrant 4 e Pedestrian (ped/h) 2 or more 150 115 Warrant 1 100 143 80 75 2 or more 100 80 70% Factor a 1 75 143 60 75 a For communities less than 10,000 population or above 40 mph (64 km/h) on major street. Only applies to Warrants 2 and 3. b The minimum minor road volume occurs when the major street volume is approximately 1,450 veh/h or at 1,050 veh/h when the community is less than 10,000 or the speed on the major road exceeds 40 mph (64 km/h). c Warrant 4 requires 190 ped/h crossing the major road in the peak hour. To compare with Warrant 3, this value was adjusted to a highest approach value by assuming a 75/25 directional distribution split. d The minimum minor road volume occurs when the major street volume is approximately 1,050 veh/h or more or at 750 veh/h when the community is less than 10,000 or the speed on the major road exceeds 40 mph (64 km/h). e Warrant 4 requires 100 ped/h crossing the major road during 4 h. To compare with Warrant 2, this value was adjusted to a highest approach value by assuming a 75/25 directional distribution split. Table 10. Comparison of vehicle and pedestrian threshold values.

number of individuals willing to walk such a distance was influenced by the number of lanes at the site (six lanes), speed and volume of traffic (high), and existing treatment (marked crosswalk only). Several of the respondents selected “yes” to the question and then commented that they walk to the nearby crossing “most of the time” or “sometimes” depending on the weather or other factors. • Reduction Criteria Based on Walking Speeds. In the current warrant, the only reduction factor is based on walking speed, and it only affects the pedestrian volume criterion.This reduc- tion factor was introduced in order to accommodate older pedestrians and persons with disabilities. Specifically, if the average walking speed is less than 4 ft/s (1.2 m/s), then a reduction of the pedestrian volume of up to 50 percent can be implemented. Chapter 6 and Appendix M include recom- mendations on walking speeds based on the research con- ducted as part of this TCRP/NCHRP study. Potential Factors Potential factors include the following: • Pedestrian Generators (Transit Stops). The closeness of a pedestrian generator is not considered within the current pedestrian signal warrant. • School Warrant. The school signal warrant has a unique feature that may lend itself to the handling of all pedestrian crossing treatments. In the school warrant, the main con- sideration is the ratio of the number of adequate gaps to the number of minutes the crossing is being used. This ratio could be used to set thresholds for various crossing treatments. • Crash Experience. As indicated in Appendix G, other countries use crash experience to justify the installation of a traffic signal. The MUTCD includes a crash experience warrant, but it is focused on vehicular crashes. Including a factor in the warranting criteria that considers safety in terms of pedestrian-related crashes, especially because of the vulnerability associated with pedestrian crashes, may be reasonable. • Counting Pedestrians on the Minor Approach with Vehicular and Bicycle Volumes. Other research has rec- ommended more global changes to the way pedestrians are handled in the signal warranting criteria (55). The recom- mendations include counting pedestrians on the minor approaches as vehicles and bicycles are counted now, which would change the vehicular-based warrants to all-mode, intersection-based warrants and would allow the pedes- trian warrant to focus on just the midblock crossing, which would make the warrant more straightforward. The largest issue to be considered is how to count pedestrians versus vehicles. The pedestrians are exposed to inclement weather conditions, have slower acceleration and speed rates result- ing in longer crossing times, and are at considerably more risk than occupants of vehicles, especially as the major street speeds increase. Therefore, developing an equiva- lency factor for pedestrians at intersections seems reason- able. Critical gaps for vehicles and pedestrians are provided in the Highway Capacity Manual and the AASHTO Green Book (23, 56). Table 11 lists the critical gaps to cross a sam- ple roadway. A pedestrian requires more time to cross an intersection than does a vehicle. To cross a two-lane road- way, a pedestrian needs 39 percent more time (factor of 1.4) than does a vehicle. At a four-lane street, a pedestrian needs twice as much time (or a factor of 2.0) than does a vehicle. Canada’s pedestrian signal procedure includes equivalent adult units with children and those with dis- abilities counting as 2.0 adults and seniors counting as 1.5 adults. The concept of counting all road users on the minor street approach is not novel to the MUTCD. The current MUTCD multi-way Stop warrant has a criterion that includes the summation of vehicles, bicycles, and pedestri- ans on the minor street approach. • Vehicle Speed. Most of the current vehicular-based traffic signal warrants include a reduction factor based on the speed of the vehicles on the major street. The pedestrian signal warrant also included the same reduction factor until the 1988 revision. • Pedestrian Delay. The HCM includes a procedure to esti- mate pedestrian delay for an unsignalized intersection. The average delay of pedestrians at an unsignalized intersection crossing depends on the critical gap, the vehicular flow rate of the subject crossing, and the mean vehicle headway. The HCM Exhibit 18-13 (reproduced as Table 12) is then used to determine the LOS of the crossing.A signal warrant could be developed based on a function of the pedestrian delay. 24 Critical Gaps Through Lanes Vehicle (s) Pedestrians (s) 2 9.0 4 15.0 Source Green Book Exhibit 9-57, assume passenger car HCM Equation 18-17, assume 12-ft (4-m) lanes, 4 ft/s (1.2 m/s) walking speed, and 3-s start up 6.5 7.5 Table 11. Critical gaps for vehicles and pedestrians at an unsignalized intersection.

Findings From the Workshop The MUTCD traffic signal warrants were developed with “a careful analysis of traffic operations, pedestrian, and bicy- clist needs, and other factors at a large number of signalized and unsignalized intersections, coupled with engineering judgment.” Research projects are periodically conducted to ensure that the traffic signal warrants reflect current opera- tional and safety needs for the different user groups. In addi- tion to researching operational and safety needs, periodic reviews of engineers’ judgment toward the traffic signal war- rants (or toward proposed revisions to the traffic signal war- rants) are needed. A study (55) in Texas recruited six DOT representatives, seven city representatives, and one consultant representative (all from Texas) to assess the appropriateness of installing a traffic signal because of pedestrian concerns at five loca- tions. The Texas study provided interesting findings; how- ever, only using engineers from one state was a concern. For this TCRP/NCHRP study, the timing and location of the 2004 Institute of Transportation Engineers Spring Confer- ence provided an opportunity to host a workshop on engi- neering judgment evaluations of pedestrian signal warrants that could include a more diverse geographic representa- tion. The workshop was held March 28, 2004, in southern California. The workshop’s objectives were to obtain opin- ions on • The traffic signal warrants; • How they related to specific locations; and • Potential treatments, including signalization, for the selected intersections. Workshop Procedures The Signal Warrant Engineering Judgment Evaluation Work- shop was held March 28, 2004. Two tours were conducted as part of the workshop. In the first tour, seven engineers partici- pated; six participated in the second. Each tour included an engineer who was very familiar with the area and could answer questions about local practices. Of the 13 participants, 9 partic- ipants came from the West Coast, one came from the North- west, one came from the East Coast, and two came from the Midwest. Each participant was provided with traffic/pedestrian data, photographs, and a sketch of the eight intersections. The traf- fic volumes were provided both in numeric format and plot- ted on a chart with the relevant curves for Signal Warrant 2 (4-hour vehicular volume) and Warrant 3 (peak hour). Tables were also provided listing the pedestrian volume (per hour and per street), intersection characteristics, and preliminary results from an analysis using the eight warrants. The group then drove to each site and reviewed the condi- tions in the field. While in the field, the participants com- pleted a questionnaire for each site. After visiting the eight sites, the tour concluded at the original hotel with a 1-hour discussion. The discussion included comments on specific sites as well as general discussion on the pedestrian signal warrant. The participants were also asked to complete a gen- eral questionnaire on the pedestrian signal warrant. Workshop Observations Details on the workshop and findings are included in Appendix J. Observations from the workshop are summa- rized below • The revised pedestrian signal warrant should consider the width of roadway being crossed. The width could either be the number of lanes or width of the roadway; however, if the number of lanes is being used, then a method to factor in the presence of bike lanes, parking lanes, and/or center turn lane needs to be included (given that all represent extra distance that a pedestrian must consider and cross). The judgment decision and gap determination become more difficult when a pedestrian is crossing a wider street. • The pedestrian signal warrant needs to consider the number of vehicles on the roadway along with the num- ber of pedestrians. When there are many pedestrians and few cars, the pedestrians can “control” the crossing by becoming a steady stream of pedestrians with insufficient gaps for vehicles to enter (for example, a site where there 25 LOS Delay/Pedestrian(s) Likelihood of Risk-Taking Behavior a A B C D E F < 5 ≥ 5 to10 > 10 to 20 > 20 to 30 >30 to 45 > 45 Low Moderate High Very High a Likelihood of acceptance of short gaps. Average Table 12. Reproduction of HCM Exhibit 18-13: LOS criteria for pedestrians at unsignalized intersections. (23)

was heavy pedestrian movement between a parking garage and a municipal building in the morning and afternoon). In this situation, a signal is not needed for the pedestrian (although one participant noted that a signal may be needed for the vehicles–i.e., the signal needs to stop the pedestrians to allow the cars to move through the cross- ing). The participants preferred having the vehicle data expressed in number of vehicles rather than gaps. • The revised warrant should consider the operating or posted speed on the major roadway. • Several participants commented on treating pedestrians and vehicles equally. • One participant noted a safety concern with crosswalks on streets with four or more lanes. These crosswalks have the potential for a “multiple threat”conflict, where a pedes- trian begins to cross in front of a vehicle stopped in the near lane but then has to avoid a vehicle in a subsequent lane that has not stopped. The participant advocated a dif- ferent set of criteria for pedestrian signals on multi-lane streets. • The participants considered the following factors during the evaluation of the eight intersections: – Pedestrian volume (92 percent); – Traffic volume (77 percent); – Speed (operating or posted) on major street (46 percent); – Number of lanes on major street (23 percent); – Other[opportunity for median refuge, crossing dis- tance, or other possible treatment (23 percent)]; – Crash history (8 percent); – Intersection versus midblock (8 percent); – Distance to nearest signal (8 percent); and – Vehicular gaps available (8 percent). • When asked what other factors should be included in the MUTCD, the only factor they listed (and that was not listed as being used in the evaluation of the eight sites— see previous bullet) was sight distance. There were several comments at individual sites where the adequacy of the available site distance was questionable, especially when on-street parking was present. Summary In the 2003 MUTCD, the pedestrian warrant for a traffic control signal considers several factors in determining the need for a signal: pedestrian volume, gaps in vehicular traffic, and walking speed (which may be used to reduce pedestrian volume). Previous studies have documented the difficulty of meeting this warrant at intersections with pedestrian cross- ing needs. A review of the literature provided insight into the current warrant as well as the signal warranting practices of other countries. In reviewing all traffic control signal war- rants, the research team noted several inconsistencies between the pedestrian warrant and vehicle-based warrants. For example, the pedestrian warrant provides a single pedestrian volume criterion, regardless of the major-street vehicle vol- ume being crossed, whereas vehicle-based warrants provide a “sliding scale” where fewer minor-street vehicles are required as the major-street vehicle volume increases. Additionally, vehicle-based warrants permit a vehicle volume reduction to 70 percent when major-street vehicle speeds exceed 40 mph (70 km/h). The research team conducted a workshop to gather engineering judgment about proposed revisions to the pedestrian warrant. In their judgment, most traffic engineers at the workshop believed the following should be considered in a revised pedestrian warrant: width of roadway being crossed, the pedestrian volume, the major-street vehicle vol- ume, and the major-street speed. The research team used these findings to develop the proposed recommendations for a revised pedestrian warrant for traffic control signals (see Appendix B). 26

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TRB's Transit Cooperative Research Program (TCRP) and National Cooperative Highway Research Program have jointly produced and published Improving Pedestrian Safety at Unsignalized Crossings. The product, which can be referred to as TCRP Report 112 or NCHRP Report 562, examines selected engineering treatments to improve safety for pedestrians crossing high-volume and high-speed roadways at unsignalized locations. The report presents the edited final report and Appendix A. TCRP Web-Only Document 30/NCHRP Web-Only Document 91 (Pedestrian Safety at Unsignalized Crossings: Appendices B to O) contains the remaining appendixes of the contractor's final report.

A summary of TCRP Report 112/NCHRP Report 562 as published in the July-August 2007 issue of the TR News is available online.

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