NYMTC Regional Pedestrian Safety Study - New York Metropolitan ...

and have geometric curvature that ensures circulatory speeds that are typically less than 30 mph.
Neighborhood traffic circles are generally at the intersections of local streets for traffic calming
or aesthetic purposes. They usually are not channelized and do not have yield control.
Roundabouts have been used successfully in Europe in recent years but have not been popular in
the United States because of bad experiences with the rotaries of the early 20 th Century. With
the older rotary, the entering vehicles had the right of way, with the result that rotaries tended to
lock up under congested conditions and to have severe safety problems. The modern roundabout
requires the entering vehicles to yield to traffic already in the circular pathway, relieving these
problems. (See NYSDOT, http://www.dot.state.ny.us/roundabouts/back.html and FHWA,
Robinson et al. 2000, http://www.tfhrc.gov/safety/00068.htm)
Roundabout: Modern roundabouts have small diameters, which require low speeds for entering
and circulating. They usually have raised islands at the center of the intersections that require
vehicles to travel in a counterclockwise direction. The islands are typically circular in shape and
frequently landscaped. Entrances to roundabouts are controlled by YIELD signs and splitter
islands to channelized traffic at the approaches. Roundabouts are particularly useful at nonstandard
intersections, for example, where more than two streets intersect or the streets are not at
90 degrees to each other.
Roundabouts prevent drivers from speeding through intersections by impeding the straightthrough
movement and forcing them to slow down to yield.
Another advantage of a roundabout for pedestrian safety is the reduction in the number of
potential vehicle-pedestrian conflicts. For example, a conventional intersection with four single
lane approaches has 16 points of potential pedestrian-vehicle conflict; a roundabout for the same
situation, has only eight points of potential conflict.
Figure 5.9 Splitter Islands and Traffic Sign for Roundabouts
NYMTC Pedestrian Safety Study 67