A modern roundabout is built with a large, circular, raised island
located at the intersection of an arterial street with one or more
crossing roadways and may take the place of a traffic signal. As
with a traffic mini-circle, traffic maneuvers around the circle
in a counter clockwise direction, and then turns right onto the
desired street. All traffic yields to motorists in the circle and
left-turning movements are eliminated. Unlike a signalized intersection,
vehicles generally flow and merge through the roundabout from each
approaching street without having to stop. Splitter islands at the
approaches slow vehicles and allow pedestrians to cross one lane
at a time.
The roundabout needs to be constructed to accommodate the needs
of pedestrians and bicyclists. Pedestrians may need to travel out
of their way to cross the intersection, but generally have a shorter
wait than with a signal and have only one direction of approaching
traffic to watch for. Unfortunately, visually impaired people have
difficulty crossing at roundabouts. This issue needs to be adequately
addressed in the design of roundabouts.
Bicyclists usually suffer the most from roundabout design. Unless
the road is very narrow (one lane in each direction), speeds very
slow, and traffic very light, bicyclists may not be able to share
the road comfortably. Marking bicycle lanes through the roundabout
has not always been shown to be safer. In larger roundabouts, an
off-road bicycle path should be created to direct cyclists to follow
the pedestrian route; while this is usually inconvenient and takes
longer, it is generally safer.
This Fort Pierce, Florida roundabout was
constructed to reduce speeding, improve safety, and enhance the
aesthetics of the community .