Model of Potential Crash Rates of Rural Roundabouts with Geometrical Features

In recent years, there has been a widespread diffusion of roundabout intersections in the Italian road network; their undoubted popularity is attributable not only to their proven performance in terms of safety but also to their guarantee of smooth traffic flow. However, safety-related requirements of geometric designs are occasionally placed in a subordinate position; therefore, the success achieved by some foreign experiences has not been reached in every area. A model of potential crash rates may indicate how to modify the geometry of intersections to ensure safety. With regard to this, an example model based on the conflict opportunity technique has been developed for estimating crash rates at rural roundabouts. The model appears to respond well to traffic conditions and the geometry of roundabouts. Development of the model and results are described and analyzed in this paper. (C) 2014 American Society of Civil Engineers.