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6C H A P T E R 2 The following sections summarize the available research for each of the eight pedestrian treat- ments initially considered for evaluation in this study. A more comprehensive literature review is provided in Appendix H. Additionally, a set of summary tables are provided at the end of Appendix H, which provide an overview of the studies for each of the eight treatments. The primary source used to compile Appendix H was a University of North Carolina (UNC) High- way Safety Research Center (HSRC) draft of the 2013 Evaluation of Pedestrian-Related Roadway Measures: A Summary of Available Research (1). Unsignalized Pedestrian Crosswalk Signs and Pavement Markings, Including Advanced YIELD or STOP Markings and Signs This treatment consists of signs or markings designed to improve the visibility of pedestrians to motorists, increase motorist yielding, and prevent multiple-threat crashes (see Figure 2-1). These treatments occur at midblock crossings or uncontrolled crosswalks at multi-lane locations located at intersections with minor stop-controlled roads. SigningâIn-Street Pedestrian Signs Nine studies were reviewed. All were behavioral studies (not crash based) and generally found in-street pedestrian signs to be an effective means of improving pedestrian safety. Results typically indicated an increase in driver yielding behavior and the number of pedes- trians using the crosswalk and a decrease in mean speeds. One study concluded that in-street pedestrian signs were more effective at intersections than they were at midblock locations (2â10). SigningâOther Signs Evaluation of pedestrian signs has shown them to be of moderate efficacy in increasing pedes- trian safety, with some variation across treatments and site characteristics. Some factors that influenced driver yielding at sign locations included the speed and volume of the roadway and whether the motorists perceived yielding as a courtesy or the law (11). Signs which are enhanced with flashing beacons or lights have been shown to be more effective when activated manually or automatically by pedestrians than those that blink continuously (11). Of the eight studies reviewed, seven indicated that the installation of various signs increased motorist yielding behavior and decreased speeding (2, 9, 11â17). Literature Review
Literature Review 7 Marked Crosswalks and Enhancements Marked crosswalks are typically installed at signalized intersections, in school zones, and at unsig- nalized intersections. The Manual on Uniform Traffic Control Devices (MUTCD) defines three types of crosswalk markings: standard parallel lines, ladder or continental stripes, and diagonal stripes. Recent research has found no safety benefit associated with various types of crosswalk markings, and the inappropriate use of marked crosswalks alone (without other substantial safety measures) can increase crash risk for pedestrians (18, 19). For example, a 2002 study (18) found that having a marked crosswalk on two-lane roads or on multi-lane (three or more lanes) roads with AADTs below 12,000 made no difference in pedestrian crash rates, compared to having no marked cross- walks. However, on multi-lane roads with AADTs above 12,000 (or above 15,000 if raised medians are present), having a marked crosswalk without other substantial treatments was associated with an increase in pedestrian crash risk, compared to having no marked crosswalk. In that study, sub- stantial treatments were considered to be such measures as a traffic signal with pedestrian signals, roadway lighting, enhanced traffic calming, and so forth. The authors of the 2002 study (18) con- cluded that it is important to not just remove marked crosswalks, but also to analyze each pedestrian crossing and determine what measures are needed to help pedestrians more safely cross the road. Advanced YIELD or STOP Markings and Signs Advanced YIELD or STOP markings are a type of pavement marking placed before a cross- walk to increase the distance at which drivers stop or yield to allow pedestrians to cross. Increas- ing the distance between yielding vehicles and pedestrians increases the ability of motorists in other lanes to see the pedestrian as the pedestrian crosses and to yield accordingly. The visibility of oncoming traffic to pedestrians is likewise improved. Eleven studies were reviewed. Ten studies indicated that advanced YIELD or STOP markings and signs reduced pedestrianâvehicle conflicts and increased motorist yielding (15, 20â29). High-Visibility Crosswalk Marking Patterns High-visibility crosswalks, when compared to the standard parallel-line crosswalks, have wider lines or additional lines to improve the conspicuity of the crosswalk to approaching drivers (see Figure 2-2). That is, the amount of white marking visible to the driver is increased by having wider longitudinal lines or by having lines parallel and perpendicular to the driverâs path. Figure 2-1. Example of advance STOP line and sign (left), advance YIELD line (sharkâs teeth) and sign (right), and a continental crosswalk. Source: www.wichita.gov
8 Development of Crash Modification Factors for Uncontrolled Pedestrian Crossing Treatments Two of the studies reviewed reported crash reduction factors for installing high-visibility crosswalks. One reported a statistically significant reduction in collisions of 37 percent (30). The other reported a reduction in pedestrian collisions of 48 percent at treatment sites, significant at the 0.05 level (31). Pedestrian Hybrid Beacons PHBs, also known as HAWK beacons (short for high-intensity activated crosswalk beacon), were developed by a Tucson traffic engineer, Dr. Richard Nassi, in the late 1990s as a means for providing safe pedestrian crossings where minor streets intersected with major arterials (32, 33). A PHB is a special type of beacon used to warn and control traffic at an unsignalized location to assist pedestrians crossing a street or highway at a marked crosswalk. The PHB signal head consists of two red lenses over a single yellow lens (see Figure 2-3). It displays a red indication to drivers when activated, which creates a gap for pedestrians to use to cross a major roadway. The PHB signal indication for motorists is not illuminated until it is activated Figure 2-2. Example of a high-visibility âladderâ crosswalk. Source: FHWA Figure 2-3. Example of a PHB. Source: PBIC
Literature Review 9 by a pedestrian, triggering the warning flashing yellow lens on the major street. After a set amount of time, the traffic signal indication changes to a solid yellow light to inform drivers to prepare to stop. The beacon then displays a dual solid red light to drivers on the major street and a walking person symbol to pedestrians. At the conclusion of the walk phase, the beacon displays an alternating flashing red light to drivers, and pedestrians are shown an upraised hand symbol with a countdown display informing them the time left to cross. The first PHB was installed in Tucson in 2000. The PHB was considered an experimental treatment until 2009, when it was included in the MUTCD. PHBs are now widely used in Tucson and have since been installed in Georgia, Minnesota, Florida, Michigan, Virginia, Arizona, Alaska, and Delaware (34). One study reviewed reported crash reduction factors for installing PHBs in Tucson, Arizona. Results of the analysis showed a statistically significant reduction in total crashes of 29 percent as well as a statistically significant reduction in pedestrian crashes of 69 percent. There was a 15 percent reduction in severe crashes; however, this result was not statistically significant (32). Rectangular Rapid Flashing Beacons The RRFB is a type of amber light-emitting diode (LED) installed to enhance pedestrian crossing signs at midblock crossings or unsignalized intersections (see Figure 2-4). RRFBs can be automated or pedestrian actuated and feature an irregular, eye-catching flash pattern to call attention to the presence of pedestrians. The RRFB was given interim approval as a crossing sign enhancement by FHWA in 2008 (35). Nine studies were reviewed. All of them indicated that RRFBs increased motorist yielding, thereby helping to reduce pedestrianâvehicle conflicts (36â44). Figure 2-4. Example of an RRFB. Source: FHWA
10 Development of Crash Modification Factors for Uncontrolled Pedestrian Crossing Treatments In-Pavement Warning Lights In-pavement lighting, which is activated by pedestrian push buttons, is sometimes used to alert motorists to the presence of a crosswalk at uncontrolled locations. Both sides of the cross- walk are lined with encased raised pavement markers, which sometimes contain LED strobe lighting (see Figure 2-5). In-pavement lighting has shown positive results such as increasing driver compliance and motorist yielding to pedestrians in Washington State, but not in Florida (45, 46). Despite some positive results with in-pavement lighting, there are several drawbacks to this method. For example, the whole system must be replaced whenever road surfacing or util- ity repairs occur. Also, in-pavement lights are generally visible to only the first car in a platoon. Headlights from oncoming traffic may obscure a driverâs view of the entire crossing. Further- more, in-pavement lighting does not indicate the direction of a pedestrianâs travel or whether people are crossing simultaneously from both sides of the road. Finally, the in-pavement flashers may be difficult to see during bright daylight hours (45, 46). Pedestrian Refuge Islands Median refuge islands, sometimes referred to as center islands, refuge islands, or pedestrian islands, are raised areas that help protect pedestrians who are crossing the road at intersections and midblock locations (See Figure 2-6). The presence of a median refuge island in the middle of a street or intersection allows pedestrians to focus on one direction of traffic at a time as they cross and gives them a place to wait for an adequate gap between vehicles. Islands are appropriate for use at both uncontrolled and signalized crosswalk locations. Where the road is wide enough and on-street parking exists, center islands can be combined with curb extensions to further enhance pedestrian safety (47). Three studies reviewed reported crash reduction factors for constructing raised medians or pedestrian islands. One study found that replacing a 6-foot painted median with a wide raised median reduced pedestrian crashes by 23 percent (49), which was consistent with findings from another study that showed pedestrian crash rates for roads with 10-foot medians were 33 per- cent lower than for roads with 4-foot painted medians (48). Finally, a before-after study was conducted to evaluate the safety effectiveness of raised pedestrian refuge islands. Researchers Source: FHWA Figure 2-5. Example of in-pavement warning lights.
Literature Review 11 found that there was a 73-percent reduction in midblock pedestrian crashes, but a 136-percent increase in total crashes. It was noted that the decrease in safety related to vehicle-island crashes might be helped by better island design and lane alignment (50). Curb Extensions Curb extensions are a way of narrowing the roadway width by extending the curb line or side- walk into the street, which results in reduced vehicle speeds, improved visibility for pedestrians and oncoming motorists, and reduced crossing distance for pedestrians (see Figure 2-7). Results of the four studies reviewed were mixed. Three of the studies indicated improve- ments in the form of reduced wait times to cross, a decreased percentage of vehicles that pass before yielding, and an increase in the distance at which vehicles yield in advance of Figure 2-6. Example of pedestrian refuge island. Source: walkinginfo.org Figure 2-7. Example of an intersection approach with a curb extension. Source: FHWA
12 Development of Crash Modification Factors for Uncontrolled Pedestrian Crossing Treatments the crosswalk (51, 53, 54). One study did not find any such positive effects of installing curb extensions (52). Raised Pedestrian Crossings Raised pedestrian crossings consist of a crosswalk that is raised above the level of the street, often at grade (see Figure 2-8). Raised pedestrian crossings tend to be applied most often on two- lane business streets in urban environments and are applied both at intersections and midblock locations. They are generally installed on lower speed roads because they are designed for speeds less than 35 mph and would not be appropriate on higher speed roads. Only one study was reviewed that considered the effect of raised pedestrian crossings on driver and pedestrian behavior. The study considered three sites in North Carolina and Maryland. Results indicated that the use of raised crosswalks resulted in lower overall vehicle speeds. The researchers also evaluated a raised crosswalk in Cambridge, Massachusetts. Results indicated an increase in the percentage of pedestrians who crossed in the crosswalk and an increase in the percentage of motorists who yielded to pedestrians in the crosswalk (55). Source: www.pedbikeinfo.org Figure 2-8. Example of raised crosswalk with an advanced STOP marking.