Intersections should be designed to accommodate safe pedestrian crossings
using tight curb radii, shorter crossing distances, and other tools as
described in this application. While right-turn slip lanes are generally
a negative facility from the pedestrian perspective due to the emphasis
on easy and fast motor vehicle travel, they can be designed to be less
problematic. At many arterial street intersections, pedestrians have
difficulty crossing due to right-turn movements and wide crossing
distances. Well-designed right-turn slip lanes provide pedestrian crossing
islands within the intersection and a right-turn lane that is designed
to optimize the right-turning motorist’s view
of the pedestrian and of vehicles to his or her left. Pedestrians
are able to cross the right-turn lane and wait on the refuge island for
their walk signal.
The problem for pedestrians is that many slip lanes are designed for unimpeded
vehicular movement. The design of corner islands, lane width, and curb
radii of right-turn slip lanes should discourage high-speed turns, while
accommodating large trucks and buses. The triangular “porkchop” corner
island that results should have the “tail” pointing to approaching
traffic. Since the traffic signal is timed based on a shorter crossing,
the pedestrian crossing time has a much smaller influence on the
timing of the signal. This design has an additional advantage for the
pedestrian; the crosswalk is located in an area where the driver is still
looking ahead. Older designs place the crosswalk too far down, where
the driver is already looking left for a break in the traffic.
Channelized right turn-lanes remain a challenge for visually-impaired
pedestrians. First, there are difficulties associated with knowing where the
crosswalk is located or knowing where to cross. Second, it is difficult
for a pedestrian who is visually-impaired to know when a vehicle has yielded
right-of way. While accessible pedestrian signals can help with these issues,
more research is currently underway through the National Cooperative Highway
Research Program (NCHRP) to further explore the problem and develop potential
solutions. Refer to NCHRP Project 3-78, Crossing Solutions at Roundabouts
and Channelized Turn Lanes for Pedestrians with Vision Disabilities (at
www4.trb.org/trb/crp.nsf/NCHRP+projects) for the latest status report.