TRCLC 14-6
Development of Decision Support Tools to Assess Pedestrian and Bicycle Safety: Field Evaluation of Driver Behavior and Traffic Operations
- PIs: Gates, Hummer – Wayne State University
- Project Period: September 1, 2014 – June 30, 2016 (22 months)
Summary:
A field study was performed at 40 uncontrolled midblock crosswalks and 26 signalized intersections on low-speed roadways selected from the areas surrounding three major urban college campuses across lower Michigan. An array of existing traffic control devices existed at the study sites, including various crosswalk marking strategies, along with additional treatments, such as pedestrian hybrid beacons (PHBs), rectangular rapid-flashing beacons (RRFBs) and single in-street R1-6 signs. The sites also collectively included a diverse set of roadway and traffic characteristics, including crossing widths, number of lanes, and median presence, along with vehicular, pedestrian, and bicyclist volumes. Three primary evaluations were performed for the midblock segments and signalized intersection study sites, including: driver yielding compliance, vehicle-pedestrian conflicts, and non-motorized traffic crash data. The yielding compliance study found that the type of crosswalk treatment has a strong influence over driver yielding compliance. While yielding compliance improves substantially when crosswalk markings are utilized, the highest compliance rates are achieved when an additional enhancement device (i.e., RRFB, PHB, or R1-6 sign), is also provided. To supplement small crash sample sizes at the study sites, Michigan statewide pedestrian and bicyclist crash data were collected and utilized to develop safety performance functions and other methods for predicting pedestrian and bicyclist crashes at road segments and intersections. Each model was developed for pedestrian and bicycle crashes based solely on vehicular AADT due to a lack of statewide non-motorized volume data. In general, the models showed that pedestrian and bicycle crashes tend to increase with increasing traffic volumes. However, even in the highest volume cases, only a fraction of crashes involved a pedestrian or bicyclist. Pedestrian and bicycle crashes were further estimated based on the respective proportion of the Michigan specific SPF models for total crashes. The primary limitation towards prediction of pedestrian and bicycle crashes is the lack of a reliable exposure data to represent the amount of pedestrian or bicyclist activity on a given segment or intersection.
Problem:
Safety performance functions (SPFs) provide a promising approach for quantifying the level for pedestrian crashes at specific intersections or road segments. The Highway Safety Manual (HSM) currently provides an aggregate pedestrian/bicycle SPF, which is based upon land use characteristics. However, since pedestrian and especially bicycle crashes are particularly rare, such an approach limits the ability to proactively identify sites with the potential for crashes that are not reflected by recent crash data. As a result, research is limited in terms of disaggregate-level studies considering the effects of motor vehicle/bicycle/pedestrian volumes, roadway geometry, and other factors on pedestrian and bicycle crashes. Furthermore, research has also been limited with respect to how these factors influence the underlying behaviors of both motorized and non-motorized road users. Therefore, alternative surrogate measures for identification of locations possessing comparatively high safety risks were investigated here.
Methods:
To address these issues, a field study was performed on low-speed roadways within Detroit, East Lansing, and Kalamazoo, Michigan to determine factors related to pedestrian and bicyclist safety risk. A variety of existing traffic control devices were considered, including various crosswalk marking strategies, along with additional treatments, including pedestrian hybrid beacons (PHBs), rectangular rapid-flashing beacons (RRFBs) and single in-street R1-6 signs, examples of which are displayed in Figure 1. A diverse set of roadway and traffic characteristics were also considered, including crossing width, number of lanes, and median presence, along with vehicular, pedestrian, and bicyclist volumes collected during the study period. A total of 66 sites were selected, including 40 uncontrolled midblock locations and 26 signalized intersections, which were selected to provide diversity among existing crosswalk treatments and roadway characteristics, along with a range of vehicular and pedestrian volumes. To ensure adequate pedestrian activity, all locations were selected on or near college campuses or commercial business districts.
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Single R1-6 |
R1-6 gateway configuration |
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Pedestrian hybrid beacon |
Rectangular rapid flashing beacon |
Driver and pedestrian behavioral observations were collected at each of the study sites using an elevated high-definition video camera (Figure 2), while historical crash data were collected for the most recent 10-year period from the Michigan State Police annual crash databases. Using these data, three primary evaluations were performed for both segments and signalized intersections, which included: driver yielding compliance, vehicle-pedestrian conflicts, and non-motorized traffic crash data, and attempts were made to examine the relationships between the behavioral measures and the crash data. Unfortunately, small sample sizes of vehicle-pedestrian conflicts and especially pedestrian/bicycle crashes limited the ability to draw meaningful conclusions from these data. Thus, to supplement small crash sample sizes at the study sites, statewide pedestrian and bicyclist crash data were collected and utilized to develop safety performance functions and other methods for predicting pedestrian and bicyclist crashes on road segments and intersections. The following sections describe the data collection and analytical methods along with results, conclusions and recommendations.
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Results:
The yielding compliance study found that the type of crosswalk treatment has a strong influence over driver yielding compliance. While yielding compliance improves substantially when crosswalk markings are utilized, the highest compliance rates are achieved when an additional enhancement device (i.e., RRFB, PHB, or R1-6 sign), is also provided. To supplement small crash sample sizes at the study sites, Michigan statewide pedestrian and bicyclist crash data were collected and utilized to develop safety performance functions (SPFs) and other methods for predicting pedestrian and bicyclist crashes at road segments and intersections. Because pedestrian and bicyclist volumes were not available statewide, each model was developed for pedestrian and bicycle crashes based solely on vehicular AADT. In general, the models showed that pedestrian and bicycle crashes tend to increase with increasing traffic volumes. However, even in the highest volume cases, only a fraction of crashes involved a pedestrian or bicyclist. Pedestrian and bicycle crashes were further estimated based on the respective proportion of the Michigan specific SPF models for total crashes.
The SPF models developed here give a general starting point for pedestrian and bicycle safety analyses. Perhaps the greatest limitation to prediction of pedestrian and bicyclist crashes, including those developed here, is the lack of reliable exposure data to represent the amount of pedestrian or bicyclist activity on a given segment or intersection. Future programs by transportation agencies or researchers should be aimed at collecting such exposure data for non-motorized users, in addition to motor vehicle traffic volumes.