Roundabouts are a safer alternative to traffic signals and stop signs. The tight circle of a roundabout forces drivers to slow down, and the most severe types of intersection crashes — right-angle, left-turn and head-on collisions — are unlikely.

Roundabouts improve traffic flow and are better for the environment. Research shows that traffic flow improves following conversion of traditional intersections to roundabouts. Less idling, in turn, reduces vehicle emissions and fuel consumption.

Roundabouts generally are safer for pedestrians. Pedestrians walk on sidewalks around the perimeter and cross only one direction of traffic at a time. Crossing distances are relatively short, and traffic speeds are lower than at traditional intersections.

-from- http://www.iihs.org/iihs/topics/t/roundabouts/topicoverview