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Human Factors Guidelines for Road Systems: Second Edition (2012)

Chapter: Chapter 11 - Signalized Intersections

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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Chapter 11 - Signalized Intersections." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Engineering Countermeasures to Reduce Red Light Running . . . . . . . . . . . . . . . . . . . . . . . .11-2 Restricting Right Turns on Red to Address Pedestrian Safety . . . . . . . . . . . . . . . . . . . . . . . . .11-4 Heuristics for Selecting the Yellow Timing Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-6 Countermeasures for Improving Accessibility for Vision-Impaired Pedestrians at Signalized Intersections . . . . . . . . . . . . . . . . . . . . . . . . . .11-8 11-1 C H A P T E R 11 Signalized Intersections

ENGINEERING COUNTERMEASURES TO REDUCE RED LIGHT RUNNING Introduction Red light running refers to drivers’ entering a signalized intersection when a red light is being presented (1). Several engineering countermeasures to reduce red light running have been proposed in McGee, Eccles, Clark, Prothe, and O’Connell (1) and Bonneson and Zimmerman (2). Some of these countermeasures reflect expert judgment, but most are supported by empirical research. Importantly, Bonneson and Zimmerman (2) note the number of driver-, intersection-, vehicle-, and environment- related factors that are correlated with red light violation frequency and likelihood. These factors include traffic volume, cycle length, advance detection for green extension, speed, signal coordination, approach grade, yellow interval duration, proximity to other vehicles, presence of heavy vehicles, intersection width, and signal visibility. Design Guidelines The following engineering countermeasures address red light running at signalized intersections. Countermeasure Type Traffic Characteristics, Operation, or Geometry Reduce approach speed by 5 mi/h Reduce delay through retiming if volume-to-capacity (v/c) ratio > 0.70 Reduce unnecessary delay through signal retiming Improve signal coordination (goal is lower delays and longer cycle lengths) Remove unneeded signals Add capacity with additional lanes or turn bays Signal Operation Increase signal cycle length by 10 s if v/c ratio < 0.60 Provide green extension (advance detection) Add protected-only left-turn phasing Motorist Information Improve signal visibility via better signal head location Improve signal visibility via additional signal head Improve signal visibility by clearing sight lines to signal Improve signal conspicuity by upgrading to 12-in. lenses Improve signal conspicuity by using yellow LEDs Improve signal conspicuity by using red LEDs Improve signal conspicuity by using back plates Improve signal conspicuity by using dual red indications Add advance warning signs (can be with or without active flashers) Add red light enforcement cameras Source: Adapted from Bonneson and Zimmerman (2) Based Primarily on Expert Judgment Based Equally on Expert Judgment and Empirical Data Based Primarily on Empirical Data Engineering Countermeasure HFG SIGNALIZED INTERSECTIONS Version 2.0 11-2

Discussion Several driver-related factors and driver behaviors are relevant to red light running and countermeasure selection. Campbell, Smith, and Najm (3) report on a study that examined fatal crashes from 1999 and 2000 included in the Fatal Accident Reporting System (FARS) and found that, of the 9,951 vehicles involved at fatal signalized- intersection crashes, 20% failed to obey the traffic signal and 13% failed to yield the right-of-way; contributing factors included alcohol, speeding, and racing. Porter and Berry (4) note that in a survey that assessed red-light-running perceptions of 880 licensed drivers, the only factor that predicted recent red light running was age group—younger respondents were more likely to run red lights. In Retting and Williams (5), video data collected by an automated camera were analyzed to identify key characteristics of red light running. The authors found that, as a group, red light runners were younger, were less likely to be wearing seat belts, and had more convictions for moving violations. McGee et al. (1) summarizes the red-light-running problem, as well as a number of engineering countermeasures, and notes that driver-related factors associated with red light running include driver expectancies, driver knowledge of the intersection and the traffic signal (e.g., the yellow interval), and the driver’s estimate of the consequences of not stopping (e.g., threat of a right-angle crash or a citation) versus stopping (e.g., threat of a rear-end crash or delays). In Bonneson and Zimmerman (2), an integrative review of past analyses and research was conducted to identify engineering countermeasures having promise for reducing the number of red light violations at intersections and/or the number of crashes associated with red light violations. The engineering countermeasures presented on the opposing page have been adapted from Bonneson and Zimmerman (2), but are also presented in slightly different formats in McGee et al. (1) and Bonneson, Zimmerman, and Brewer (6). Design Issues McGee et al. (1) make an important distinction between intentional and unintentional red light running that can affect countermeasure selection and development. Specifically, McGee et al. (1) note that intentional red light runners are most affected by enforcement countermeasures (such as red light cameras) while unintentional red light runners are most affected by engineering countermeasures. Red light cameras are frequently employed as enforcement countermeasures to reduce red light running. In Council, Persaud, Eccles, Lyon, and Griffith (7), an empirical Bayes before/after approach was used to determine effectiveness of red light cameras at 132 treatment sites. The authors report that red light cameras were associated with decreased right-angle crashes and increased rear-end crashes, with an aggregate crash cost-benefit associated with the use of red light cameras. Also, the presence of warning signs at both the city limit and the intersection was associated with a larger benefit than signs at just the intersection; high publicity was also associated with higher benefits. Caveats associated with the study were that other variables (driver, traffic volumes, temporal, environmental, signal) were either not included in the analyses (uncontrolled or confounded) or not associated with a large enough sample to detect an effect. Also, the analyses could not distinguish the effects of other improvements occurring at the same location as the red light cameras. Cross References Heuristics for Selecting the Yellow Timing Interval, 11-6 Key References 1. McGee, H., Eccles, K., Clark, J., Prothe, L., and O’Connell, C. (2003). Making Intersections Safer: A Toolbox of Engineering Countermeasures to Reduce Red-Light Running. Washington, DC: ITE. 2. Bonneson, J., and Zimmerman, K. (2004). Red-Light-Running Handbook: An Engineer's Guide to Reducing Red-Light-Related Crashes. College Station: Texas Transportation Institute. 3. Campbell, B.N., Smith, J.D., and Najm, W.G. (2004). Analysis of Fatal Crashes Due to Signal and Stop Sign Violations (DOT HS 809 779). Cambridge, MA: Volpe National Transportation Systems Center. 4. Porter, B.E., and Berry, T.D. (2001). A nationwide survey of self-reported red light running: Measuring prevalence, predictors, and perceived consequences. Accident Analysis & Prevention, 22, 735-741. 5. Retting, R.A., and Williams, A.F. (1996). Characteristics of red light violators: Results of a field investigation. Journal of Safety Research, 27(1), 9-15. 6. Bonneson, J., Zimmerman, K., and Brewer, M.A. (2002). Engineering Countermeasures to Reduce Red-Light-Running (FHWA/TX- 03/4027-2). College Station: Texas Transportation Institute. 7. Council, F.M., Persaud B., Eccles, K., Lyon, C., and Griffith, M.S. (2005). Safety Evaluation of Red-Light Cameras. (FHWA-HRT-05-048). McLean, VA: FHWA. 11-3 HFG SIGNALIZED INTERSECTIONS Version 2.0

RESTRICTING RIGHT TURNS ON RED TO ADDRESS PEDESTRIAN SAFETY Introduction This guideline describes approaches for implementing restrictions on right turn on red (RTOR) movements with the objective of reducing conflicts between pedestrians and right-turning vehicles. The MUTCD (1) provides six situations where RTOR should be restricted, and three of these specifically address pedestrians: (1) where an exclusive pedestrian phase exists, (2) where significant pedestrian conflicts result from RTORs, and (3) where there is significant crossing activity by pedestrians who are children, are elderly, or have disabilities. Typically, around 40% of drivers do not stop completely before making a RTOR (2). Of those drivers that do stop, many will stop beyond the marked stop line and block the pedestrian crosswalk while waiting to turn. This blocking of the crosswalk can impede pedestrian movements or cause pedestrians to walk outside of the marked crosswalk. Also, pedestrians may yield the right-of-way before entering the intersection and may not have time to clear the intersection before the signal changes. This is especially problematic for older pedestrians who take longer to cross. Design Guidelines Restrictions on RTOR can be used to reduce conflicts between pedestrians and turning vehicles, and to increase the likelihood that drivers will stop before turning right at an intersection. The most effective method is to base turning restrictions on time of day (e.g., from 6:00 am to 6:00 pm). Basing restrictions on the presence of pedestrians at the intersection will also reduce conflicts; however, this approach appears to be significantly less effective than time-based restrictions. Based Primarily on Expert Judgment Based Equally on Expert Judgment and Empirical Data Based Primarily on Empirical Data The table below shows examples of different implementations for RTOR signage. Countermeasure Example Effectiveness Most effective Effective with low to moderate volume of RTOR Effective when sight distances are problematic Effective Countermeasure Key Features Preferred Application Red Ball on NTOR Sign More “eye catching” This is an effective signing approach in most situations. Larger 30 x 36 Size More conspicuous On the far side of a wide intersection. “When Pedestrians are Present” Addition Permits RTOR but requires drivers to yield to pedestrians Sites with low to moderate volumes of RTOR and pedestrian volumes that are low or occur primarily during intermittent periods. Offset Stop Bar Provides improved sight distance to RTOR vehicle Sites with two or more approach lanes, heavy truck or bus traffic, or unusual geometries. Variable Blank-Out Signs Lit only during times that RTOR is prohibited When pedestrian protection is critical during certain time periods (e.g., in school zones) or during a signal cycle when a separate, opposing left-turn phase may conflict with an unsuspecting RTOR driver. “Look for Turning Vehicles” Pavement Markings Can make pedestrians more cautious Sites with particular problems involving pedestrian crashes or conflicts with RTOR vehicles. HFG SIGNALIZED INTERSECTIONS Version 2.0 11-4

Discussion With regard to conditional RTOR restrictions, restrictions based on certain times of day (time-restricted) and those based on the presence of pedestrians (pedestrian-restricted) increase drivers’ stopping at the stop line (3). However, the time-restricted implementation appears to be more effective both when pedestrians are present and when they are not. Retting, Nitzburg, Farmer, and Knoblauch (3) found that the pedestrian-restricted implementation significantly reduced RTOR when pedestrians were present (by 11%), but they still occurred 57% of the time. In contrast, time- restricted implementation led to a much greater reduction (from 77% to 19%). Additionally, the time-restricted implementation significantly increased the number of drivers that stopped before making a RTOR, while the pedestrian-restricted implementation did not. There was also a difference in terms of pedestrian capacity. In particular, the time-restricted implementation significantly reduced the number of pedestrians that yielded to drivers, but the pedestrian-restricted implementation did not. Time-restricted implementations can be based on when pedestrian–turning vehicle crashes are most likely to occur. In particular, Stutts, Hunter, and Pein (4) found that 80% of intersection crashes involving pedestrians and turning vehicles occur between 6:00 am and 6:00 pm. Regarding the relative effectiveness of different signage options, Zeger and Cynecki (5) compared different approaches and found that the NO TURN ON RED (NTOR) sign with a red ball was more effective than the standard black and white NTOR sign. Also, NO TURN ON RED WHEN PEDESTRIANS ARE PRESENT signs were effective at sites with moderate to low volumes of RTOR vehicles, although the legend was found to be difficult to read when located adjacent to the signal or on the far side of the intersection. Lastly, the presence of an offset stop bar improved motorist compliance, reduced conflicts with cross-street traffic, and was recommended for use on multilane approaches under some conditions (see Zeger and Cynecki (5)). Another issue to consider is the use of electronic signing, such as blank-out NTOR signs that are lit only during the times that turns are restricted. In Zeger and Cynecki (5), an electronic NTOR blank-out sign was slightly more effective, although considerably more costly, than traditional signs. Similarly, another study found that sites with variable message signs were effective in lowering incidence of motorists who illegally turned right on red. This study did not compare the effectiveness to traditional signs, so it is unclear if the benefits outweighed the additional costs of the variable message signs. Design Issues Several factors can diminish the effectiveness of RTOR restrictions on driver compliance (see Zeger and Zeger (6)): Confusing partial prohibitions (e.g., 7-9 am and 4-6 pm, except Sundays) Far-side or hidden NTOR signs Long cycle lengths Confusing multi-leg intersections NTOR that does not appear to be justified given the traffic conditions Also, inconsistent placement of RTOR signs from intersection to intersection can reduce the effectiveness of the signs. Cross References Determining Intersection Sight Distance, 5-6 Sight Distance at Right-Skewed Intersections, 10-8 Key References 1. FHWA (2009). Manual on Uniform Traffic Control Devices (MUTCD). Washington, DC. 2. ITE (1992). Driver behavior at right-turn-on-red locations. ITE Journal, 62(4), 18-20. 3. Retting, R.A., Nitzburg, M.S., Farmer, C.M., and Knoblauch, R.L. (2002). Field evaluation of two methods for restricting right turn on red to promote pedestrian safety. ITE Journal, 72(1), 32-36. 4. Stutts, J.C., Hunter, W.W., and Pein, W.E. (1996). Pedestrian-vehicle crash type: An update. Transportation Research Record, 1538, 68-74. 5. Zegeer, C.V., and Cynecki, M.J. (1986). Evaluation of countermeasures related to RTOR accidents that involve pedestrians. Transportation Research Record, 1059, 24-34. 6. Zegeer, C.V., and Zegeer, S.F. (1988). NCHRP Synthesis of Highway Practice 139: Pedestrians and Traffic-Control Measures. Washington, DC: Transportation Research Board. 11-5 HFG SIGNALIZED INTERSECTIONS Version 2.0

HEURISTICS FOR SELECTING THE YELLOW TIMING INTERVAL Introduction The yellow timing interval refers to the duration of the yellow signal indication; the yellow timing interval is also referred to as the “yellow change interval” in a number of sources. The yellow signal warns oncoming traffic of an imminent change in the right-of-way assignment (1,2). Most traffic engineering sources (1,2,3) recommend a yellow change interval of 3 to 5 s duration. Increases to a given yellow timing interval are usually implemented in order to decrease instances of red light running. Van Winkle (4) notes that the many variables influencing the selection of yellow timing intervals include approach speed, intersection width, vehicle length, vehicle deceleration level, visibility of traffic signals, response time of the driver, degree of enforcement, specific laws, and motorist attitudes; this source also recommends using a consistent interval to eliminate driver uncertainty as a variable. Design Guidelines Pline (1) and ITE Technical Council Committee 4TF-1 (5) indicate that the following formula can be used to calculate the yellow timing interval time plus the red clearance interval time. Metric Values [English Values] CP = t V 2a + 2Gg W + L V+ + Metric: a = deceleration, m/s2 (typically 3.1 m/s2) G = gravity @ 9.8 English: a = deceleration, ft/s2 (typically 10 ft/s2) G = gravity @ 32.2 Where: CP = non-dilemma change period (Change + Clearance Intervals) t = perception-reaction time (nominally 1 s) V = approach speed, m/s [ft/s] g = percent grade (positive for upgrade, negative for downgrade) a = deceleration, m/s2 (typical 3.1 m/s2) [ft/s2 (typical 10 ft/s2)] W = width of intersection, curb to curb, m [ft] L = length of vehicle, (typical 6 m) [ft (typical 20 ft)] From Pline (1): Yellow timing intervals should generally have a duration of 3 to 5 s. If more than 5 s is required, a red clearance interval is used. Because a longer interval may encourage drivers to use the yellow as a part of the green interval, a maximum of about 5 s for the yellow timing interval is generally used. When the calculation for the yellow timing interval yields a time greater than 5 s, a red clearance interval generally provides the additional time. Given the many variables included in the formula above (estimates for reaction time, vehicle deceleration, grades, and intersection clearing time), engineering judgment should be used to apply the results of these calculations toward determining the yellow change interval. FHWA (2) notes that the yellow timing interval “may be followed by an optional red clearance interval to provide additional time before conflicting traffic movements, including pedestrians, are released”; it further notes that this all-red interval should not exceed 6 s. Based Primarily on Expert Judgment Based Equally on Expert Judgment and Empirical Data Based Primarily on Empirical Data The figure below depicts the dilemma zone when a driver approaching a signalized intersection is faced with a green light that changes to yellow (adapted from Pant, Cheng, Rajaopal, and Kashayi (8)). X = s Minimum Stopping Distance X = c Maximum Clearing Distance Dilemma Zone HFG SIGNALIZED INTERSECTIONS Version 2.0 11-6

Discussion Driver behaviors relevant to the selection of a yellow timing interval have been studied by the transportation research community for many years. Tijerina, Chovan, Pierowicz, and Hendricks (6) note that crash data for signalized intersections show that the decision to proceed through a yellow signal likely represents a source of problems for many drivers.In particular, the most common contributing factors include deliberately running the signal (40%), either because drivers failed to obey the signal (23.1%) or tried to beat the signal (16.2%). The next most common contributing factor was driver inattention (36.4%). A critical aspect of driver behavior related to the yellow timing interval is associated with the “dilemma zone.” When a driver sees a green signal changing to yellow, a dilemma zone is created. The dilemma zone represents the portion of the roadway between (1) the clearing distance to the intersection (the distance the vehicle travels between the time the signal changes to yellow to the time the signal changes to red) and (2) the stopping distance (the distance traveled by the vehicle between the time the signal changes to yellow to the time when the vehicle actually stops) when the stopping distance is greater than the clearing distance. The dilemma zone is therefore not a fixed area. While in the dilemma zone, the driver must assess the situation and then decide whether to stop or proceed through the intersection based on that assessment. A recent task analysis of driver behavior while traveling straight through an intersection on a yellow signal (7) confirms that the decision to stop or not is a complex one. As noted in Richard, Campbell, and Brown (7), there are two reasons drivers run the signal (and risk a right-angle crash) when the appropriate action would be to stop: (1) they correctly assess the situation as unsafe and then make a bad decision to go anyway, or (2) they incorrectly assess the situation as safe (perhaps because the driver missed relevant information) and make the logical—but incorrect—decision to proceed. The latter case is similar to driver inattention, whereby drivers also fail to adequately perceive and process the necessary situational information. Overall, it is clear that dilemma zone situations provide limited options for drivers not only because they have an extremely limited amount of time to perform several tasks, but also because they are limited in the types of actions they can safely or legally take. Pant et al. (8) carried out a study to test and implement a dilemma zone protection technique (placement of detectors leading up to the intersection and the use of a green extension of 1 to 5 s) at three high-speed intersections in Ohio. The authors report that the use of detectors, combined with a 3-s extension, can provide drivers with some dilemma zone protection. They also note that differences among intersections with respect to vehicle speeds, operational characteristics, and geometries suggest that specific solutions are unique to individual intersections. Design Issues The possibility of long-term driver adaptation to longer yellow timing intervals has not been extensively studied. Specifically, the driver behavior and crash rates associated with changes in the yellow timing interval seen in many of the field studies in this area may reflect only temporary effects that will recede once drivers acclimate to the longer yellow. Cross References Engineering Countermeasures to Reduce Red Light Running, 11-2 Key References 1. Pline, J.L. (Ed.). (2001). Traffic Control Devices Handbook. Washington, DC: ITE. 2. FHWA (2009). Manual on Uniform Traffic Control Devices (MUTCD). Washington, DC. 3. Pline, J.L. (Ed.). (1999). Traffic Engineering Handbook, Fifth Edition. Washington, DC: ITE. 4. Van Winkle, S.N. (1999). Clearance interval timing—a viewpoint. Transportation Frontiers for the Next Millennium: 69th Annual Meeting of the Institute of Transportation Engineers (p. 3). Washington, DC: ITE. 5. ITE Technical Council Committee 4TF-1. (1994). Determining Vehicle Signal Change and Clearance Intervals (IR-073). Washington, DC: ITE. 6. Tijerina, L., Chovan, J., Pierowicz, J., and Hendricks, D. (1994). Examination of Signalized Intersection, Straight Crossing Path Crashes, and Potential IVHS Countermeasures (DOT HS 808 143). Washington, DC: National Highway Traffic Safety Administration. 7. Richard, C.M., Campbell, J.L., and Brown, J.L. (2006). Task Analysis of Intersection Driving Scenarios: Information Processing Bottlenecks (FHWA-HRT-06-033). Washington, DC: FHWA. 8. Pant, P.D., Cheng, Y., Rajaopal, A., and Kashayi, N. (2005). Field Testing and Implementation of Dilemma Zone Protection and Signal Coordination at Closely-Spaced High-Speed Intersections. Columbus, OH: Department of Transportation. 11-7 HFG SIGNALIZED INTERSECTIONS Version 2.0

HFG SIGNALIZED INTERSECTIONS Version 2.0 11-8

Discussion Curb ramps: Aligning themselves with the crosswalk and staying within it are some of the biggest challenges that vision- impaired pedestrians face at intersections. One study found that only 66% to 75% of pedestrians started within the crosswalk, started from an aligned position, traveled within the crosswalk, and ended within the crosswalk (2). Two factors that contribute to these problems are large-radius corners that eliminate important cues for alignment, and curb ramps that do not line up with the crosswalk, which make finding the crosswalk more difficult for vision-impaired pedestrians (3). Factors that help vision-impaired pedestrians detect the crosswalk location include a ramp slope that has a steep angle, an abrupt rate of change in the slope between the approach to each curb and the ramp itself, and curb ramps aligned with the crosswalk (4). O’Leary, Lockwood, and Taylor (5) found that domed surfaces were far more detectable than rough aggregate surfaces and that a majority of the totally vision-impaired participants failed to detect either of two exposed rough aggregate surfaces. Signal timing: Vision-impaired pedestrians can cross at the same speed as other pedestrians (4 ft/s), but they require additional time before crossing to determine that it is safe to cross (by listening to the near-side parallel vehicle surge). This additional time can result in pedestrians leaving the curb during the clearance interval after the initial “walk” interval has passed. Bentzen, Barlow, and Bond (2) found that mean starting delay ranged from 5 to 8 s and resulted in 26.2% of all crossings being completed after the onset of perpendicular traffic. APS: As indicated in the guideline, recommended characteristics for APSs (e.g., location, tones, speech messages) and associated pushbuttons (e.g., locator tone, tactile arrow, information message) are covered in detail in Barlow et al. (1). These recommendations address important difficulties that vision-impaired pedestrians encounter with APSs and pushbuttons. In particular, common problems with APSs include (1) identifying which crosswalk had the signal, (2) hearing a signal that is too quiet, (3) remembering which sound is for which direction, and (4) finding the APS (6). Additionally, common problems with pushbuttons include (1) not being able to determine if a pushbutton is present, (2) locating the pushbutton, (3) identifying which crosswalk is actuated by the pushbutton, and (4) having insufficient time to prepare for crossing because pushbuttons are located too far from the crosswalk (6). Design Issues The MUTCD (7) states that APS implementation should be based on engineering studies that consider the following factors: (1) potential demand for accessible pedestrian signals; (2) a request for accessible pedestrian signals; (3) traffic volumes during times when pedestrians might be present, including periods of low traffic volumes or high turn-on-red volumes; (4) the complexity of traffic signal phasing; and (5) the complexity of intersection geometry. Additional guidance about locations that may require APSs are presented in Barlow et al. (1) and include the following: Intersections with vehicular and/or pedestrian actuation Very wide crossings Non-rectangular or skewed crossings T-shaped intersections High volumes of turning vehicles Major streets at intersections with low-traffic minor streets (an APS may be needed for crossing the major street) Split phase signal timing Exclusive pedestrian phasing, especially where right-turn-on- red is permitted A leading pedestrian interval Cross References Countermeasures for Improving Accessibility for Vision-Impaired Pedestrians at Roundabouts, 10-10 Key References 1. Barlow, J.M., Bentzen, B.L., and Tabor, L.S. (2003). Accessible Pedestrian Signals: Synthesis and Guide to Best Practices. Final Report, NCHRP Project 3-62. Berlin, MA: Accessible Design for the Blind. http://www.walkinginfo.org/aps 2. Bentzen, B.L., Barlow, J.M., and Bond, T. (2004). Challenges of unfamiliar signalized intersections for pedestrians who are blind: Research on safety. Transportation Research Record, 1878, 51-57. 3. Barlow, J.M. (2004). Orientation and alignment for street crossing: pedestrians who are blind or visually impaired. Curb Ramp and Intersection Wayfinding Workshop. Washington, DC: ITE. 4. Bentzen, B.L., and Barlow, J.M. (1995). Impact of curb ramps on the safety of persons who are blind. Journal of Visual Impairment & Blindness, 89(4), 319-328. 5. O'Leary, A.A., Lockwood, P.B., and Taylor, R.V. (1996). Evaluation of detectable warning surfaces for sidewalk curb ramps. Transportation Research Record, 1538, 47-53. 6. Bentzen, B.L., Barlow, J.M., and Franck, L. (2000). Addressing barriers to blind pedestrians at signalized intersections. ITE Journal, 70(9), 32-35. 7. FHWA (2003). Manual on Uniform Traffic Control Devices (MUTCD). Washington, DC. 11-9 HFG SIGNALIZED INTERSECTIONS Version 2.0

Next: Chapter 12 - Interchanges »
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 600: Human Factors Guidelines for Road Systems: Second Edition provides data and insights of the extent to which road users’ needs, capabilities, and limitations are influenced by the effects of age, visual demands, cognition, and influence of expectancies.

NCHRP Report 600 provides guidance for roadway location elements and traffic engineering elements. The report also provides tutorials on special design topics, an index, and a glossary of technical terms.

The second edition of NCHRP 600 completes and updates the first edition, which was published previously in three collections.

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