Click for next page ( 20


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 19
19 Many of the early problems have been resolved through the past 10 years of experience, but some cities continue to be cautious in specifying more in-roadway warning lights until they have long-term experience. Some cities have noted their preference for overhead flashing beacons instead of in-road- way lights because of poor visibility issues when traffic is queued in front of the in-roadway lights (37, 39). Another concern is that in very bright sunlight, the flashing lights are difficult for drivers to see. For most of the installations, in-roadway warning lights have increased driver yielding to the 50 to 90 percent range (38, 40-44). Additionally, the in-roadway warning lights typ- ically increase the distance that motorists first brake for a pedestrian crossing, indicating that motorists recognize the pedestrian crossing and the need to yield sooner (40-43). These results have been even more dramatic at night when the in-roadway warning lights are highly visible. For a few instal- lations, driver yielding decreased or did not increase above 30 percent (38, 45). The research team hypothesizes that these installations were most likely inappropriate and other cross- ing treatments would have been more effective. The research team did not include in-roadway warning lights in this TCRP/NCHRP project's field studies because of the abun- dance of evaluation results in the literature. Motorist Warning Signs and Pavement Markings Figure 10. Pedestrian crossing flags in Salt Lake City, Utah. Motorist warning signs and pavement markings used as pedestrian crossing treatments can take many shapes and forms; examples are as follows: As indicated, several of the crossing treatments show more Animated or roving eyes, promise than others. Advance yield lines place the traditional Advance yield or stop lines, stop or yield line 30 to 50 ft (9.1 to 15.2 m) in advance of the Crossing flags carried by pedestrians (see Figure 10), crosswalk and are often accompanied by Yield Here to Pedes- Yield to Pedestrian and Stop Here for Pedestrian signs, and trian signs. Advance yield lines address the issue of multiple Internally illuminated crosswalk signs. threat crashes on multi-lane roadways, where one vehicle may stop for a crossing pedestrian but inadvertently screens the The experience with these types of warning signs and pedestrian from the view of vehicles in other lanes. Several pavement markings has generally been modest, with a few studies have documented that advance yield lines decrease treatments showing more promise than others. The strength pedestrian-vehicle conflicts and increase driver yielding at of the message that these traffic control devices sends to greater distances from the crosswalk (28, 46-48). motorists is mostly considered a warning (i.e.,"watch out for In-street pedestrian crossing signs and high-visibility signs pedestrians" or "avoid pedestrians"). In many cases, the and markings were two types of treatments included in this research team hypothesizes that motorists receive these TCRP/NCHRP project's study sites. The field studies indicated warning messages and consider yielding or stopping for that in-street signs had relatively high motorist yielding pedestrians as a courtesy and not the law (it is the law in (ranged from 82 to 91 percent, for an average of 87 percent); many states). The research team further hypothesizes that however, all three study sites were on two-lane streets with motorists are less willing to extend this "courtesy" to pedes- posted speed limits of 25 or 30 mph (40 or 48 km/h). The trians on high-speed, high-volume roadways because they results for high-visibility signs and markings also demon- think (1) they are being delayed unnecessarily and (2) these strated the effects of higher posted speed limits. One site with high-speed, high-volume roadways are the domain of auto- high-visibility signs and markings and a posted speed limit of mobiles and not pedestrians. 25 mph (40 km/h) had a motorist yielding value of 61 percent.