Cover Image

Not for Sale

View/Hide Left Panel
Click for next page ( 11

The National Academies of Sciences, Engineering, and Medicine
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 10
10 CHAPTER 1 Introduction This report explores concerns about the accessibility of of the crosswalk, can be difficult, particularly when other two complex intersection forms to pedestrians who are blind: sounds mask the sounds of approaching or yielded vehicles. intersections with channelized turn lanes (CTLs) and mod- Another key challenge for roundabouts and CTLs is that they ern roundabouts. Crossing challenges for blind pedestrians often carry higher volumes than other typical two-way stopped have been established through research (e.g., Guth et al. 2005, control (TWSC) and all-way stopped control (AWSC) inter- Ashmead et al. 2005, Schroeder et al. 2006) for both types of sections, which are also unsignalized. intersections. The emphasis of this project was on the identi- In addition to determining when to cross the road, pedestri- fication of crossing treatments that can assist blind travelers ans with vision impairments must identify where to cross and in accessing these facilities at reasonable risk and with a rea- which way to walk during the crossing, and must determine sonable amount of delay. when they have arrived at their destination curb or island (Guth Channelized turn lanes are a very common intersection et al. 1989). These challenges are common to all pedestrian treatment, intended to allow heavy right-turning movements crossings, but are exacerbated at roundabouts and CTLs due to to bypass an otherwise signalized intersection. Crosswalks at the unexpected, non-perpendicular alignment of the crosswalk. CTLs are oftentimes unsignalized in the United States, and While prior research has demonstrated and documented pedestrians are therefore required to make crossing decisions the crossing challenges for blind pedestrians at these facilities independently, without assistance from an accessible pedes- (e.g., Guth et al. 2005, Ashmead et al. 2005, Schroeder et al. trian signal (APS) or other audible device. 2006), it has failed to develop and test crossing solutions that Modern roundabouts are increasingly being adopted by would improve the accessibility of these facilities. The objec- the transportation community in the United States due to their tive of NCHRP Project 3-78A was to fill that void and evaluate ability to process balanced and unbalanced traffic patterns, a range of pedestrian crossing treatments in controlled field their aesthetic appeal, and most importantly, their documented experiments with the goal of providing decision support to safety benefits (e.g., Rodegerdts et al. 2007, FHWA 2000, engineers and policy makers. Persaud et al. 2000). Similar to CTLs, there remain concerns about the accessibility of modern roundabouts to certain Safety Is Not Synonymous groups in the pedestrian community. Of particular concern with Access is the accessibility to pedestrians with blindness or low vision (U.S. Access Board 2003). The underlying premise of this research is that while safety Roundabouts and CTLs, like other unsignalized inter- and access of a facility are related, the two terms are not syn- sections, present challenges that are different from signalized onymous. A facility could be considered safe if the crash rate intersections for individuals with blindness and other visual at the facility is low. However, effective access must be judged impairments. Roundabouts have relatively free-flowing traf- by the extent to which any individual or group of individuals fic patterns, and they lack the more predictable pattern of traf- limits its use of a facility based on a real or perceived belief that fic movement that is associated with signalized intersections. the facility is unsafe or extraordinarily difficult to use. The This reduced predictability sometimes makes it difficult to absence of recorded pedestrian crashes, especially those involv- judge when it is safe to cross at roundabout crossings using ing older pedestrians, children, or those with visual and/or auditory cues alone. Judging gaps in traffic that afford cross- physical impairments, does not constitute proof that a facil- ing, or determining that vehicles have yielded just upstream ity is accessible, nor does the presence of crashes constitute