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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
