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vehicles, the blind pedestrian must wait until traffic is stopped the two traffic streams typically move perpendicularly to each
or until there is no traffic approaching from either direction on other, presumably making it easier for someone who is blind
the through street. to interpret directional traffic movements. Finally, the contin-
The downstream crosswalk location creates different issues. uous flow of traffic circulating the roundabout can create a
At the downstream location, drivers of vehicles in the turn lane difficult auditory environment, and the listening task is com-
are more likely to be looking to their left at vehicles approach- plicated by elevated levels of ambient noise.
ing on the major street and not to their right where a pedes- All of these factors may contribute to accessibility challenges
trian may be waiting to cross from the curb. Where volumes at roundabouts and CTLs. Research in this area and the work
on the major street are low and gaps required to merge from of this project have divided the crossing task into four princi-
the turn lane are readily perceived, vehicles may accelerate pal areas that guide the understanding of the challenges faced
as they approach the downstream exit, lessening the likeli- by pedestrians who are blind. Additionally, the four areas
hood that they will yield to pedestrians. However, where vol- require different treatments to improve targeted aspects of
umes on the downstream departure leg are high, there may pedestrian accessibility. The four crossing components are:
be times in the signal cycle when vehicles in the channelized
lane are regularly stopped to wait for a gap in traffic. Sighted 1. Locating the crosswalk,
pedestrians often cross between stopped vehicles at these times, 2. Aligning to cross,
but blind pedestrians may have difficulty determining that 3. Identifying a crossing opportunity, and
vehicles have stopped. Higher speeds and lower likelihoods 4. Maintaining alignment during crossing.
of yielding to pedestrians are also more likely when an accel-
eration lane is provided at the CTL exit. In the following, each component is discussed in detail.
Facilities built since 2001 compliant with the American
with Disabilities Act (ADA) include a curb ramp with trun-
Locating the Crosswalk
cated-dome detectable warnings that delineate the edge of
the roadway. If the crosswalk and ramp are located upstream A pedestrian approaching an intersection needs to be able to
or downstream within the CTL, the ramp may terminate identify the location of the crosswalk. For standard orthogonal
into the radius of the curve, which is not perpendicular to the intersections, this is a fairly simple task since the curb ramps
crosswalk. Blind pedestrians may experience problems with are located in the vicinity of the corner of the intersection, usu-
identifying the crossing location and alignment at all cross- ally within 15 ft if the turning radius is not significant. How-
walks at channelized turn lanes because of the curvature. ever, at roundabouts and CTLs, there is no distinct point of
interest (such as the corner) where a pedestrian would expect
a crosswalk to be located. Instead, the auditory environment
Accessibility Challenges
from nonlinear traffic patterns can be difficult to navigate com-
Recent research on the crossing performance of people who pared to the typical orthogonal intersection.
are blind at complex intersections demonstrates that there are For roundabouts, finding the crosswalk is highly depend-
unique challenges for this population (Ashmead et al. 2005, ent on the direction of travel and the side of the roundabout
Guth et al. 2005). Complex intersections, including round- being approached. For instance, a pedestrian wishing to turn
abouts and channelized turn lanes, present some unique chal- left with traffic approaching the roundabout from behind her
lenges for pedestrians with vision impairments. The traffic would have the crosswalk on her left, similar to a standard
control strategy at a roundabout entry leg is typically a yield orthogonal intersection. Even so, the circulating traffic does
sign, and many drivers are able to enter the circle without the not provide a consistent point of reference to begin looking
requirement to come to a full stop. Similarly, traffic exiting for the crossing location. The task of walking straight through
the roundabout is free-flowing (often accelerating), resulting a roundabout intersection poses further challenges. The pedes-
in largely uninterrupted traffic flow at the exit portion of the trian must be aware that she must navigate around the circle
crosswalk. Traffic patterns at CTLs are similar in that the right- via sidewalk cues or landscaping and then locate the crossing
turning movement is largely free-flowing. Crosswalks at both location a significant distance from where the typical crossing
types of facilities are typically not signalized, and the task of would be located at a standard intersection. Since vehicles do
identifying crossing opportunities is thus unassisted. Depend- not move in a perpendicular fashion with other vehicles, the
ing on the geometric design and the location of the crosswalk, pedestrian may need repeated attempts to identify the crossing
vehicle speeds may be relatively high, and the auditory inter- location, which can be time-consuming and dangerous.
pretation is complicated because vehicles are moving on a cir- For similar reasons, CTLs can be challenging to a blind
cular path (Ashmead et al. 2005). At signalized intersections, pedestrian. The unusual geometry associated with the large
