State-of-the-Art Design of Roundabouts

Abstract

In the United States roundabouts are becoming more popular. European improvements in design, operations, and traffic regulations have led to safer performance in roundabouts than in conventional intersections. Consequently, capacity and delay have also improved. More uniform practices have emerged, particularly the yield-at-entry traffic rule and vehicle path deflection through the roundabout. For the benefit of U.S. planners and designers, a synthesis and recommendations based on up-to-date international and domestic practices are provided. Those practical design issues are concisely discussed: justification; safety and accident prediction; capacity; delays; location; design considerations (design vehicle, design speed, sight distance, deflection, central island, circulating roadway, entries and exits, splitter islands, signing, and landscaping); bicycle considerations; pedestrian considerations.