Roundabouts, traffic flow and public opinion

July 2006

Roundabouts can provide substantial safety and traffic flow benefits compared with conventional intersections, but they often are opposed in the planning stage by local residents and elected officials who question their effectiveness. The purpose of the present study was to measure public opinion before and after construction of roundabouts in several communities and to evaluate the impact of roundabout construction on traffic flow. Three communities where stop-sign- or traffic-signal-controlled intersections were replaced with roundabouts in 2004 were the subjects of this research. Overall, 36 percent of drivers supported the roundabouts before construction compared with 50 percent shortly after construction. Roundabouts had very positive effects on traffic flow. Average intersection delays during peak hours at the three sites were reduced by 83-93 percent. Traffic congestion, as measured by the vehicle-to-capacity ratio, was reduced by 58-84 percent. These results provide further evidence that roundabouts can improve traffic flow and that public support for roundabouts increases after they are in place.