Author(s)

G. Guido & A. Vitale

Abstract

In recent years, intersections planned with roundabouts have had a remarkable diffusion, especially in urban areas. Compared to conventional intersections, this system is suitable to improve road safety. In Italy, in spite of many positive experiences that have been made, still there is no defined norm and regulation for roundabouts. This research can give guidelines for norms and roundabout design, through the development of a generalized behavioural model. In particular, the proposed model simulates user’s lane changing choices inside the roundabout. In this paper, a behavioural Nested Logit model is proposed. Preliminary results, obtained through application on some urban roundabouts, showed that roundabouts perform depending not only on the flow in the weaving area and the length of the weaving area, but also on the speed of vehicles changing lanes and critical gaps. The relationship between these quantities and intersection capacity can be traduced: • under the same conditions of gap acceptance, changing lane probability increases proportionally to the speed difference between the vehicle that changes lane and the vehicle behind on the adjoining lane; • with the same length of weaving area, the capacity of the intersection increases inversely proportional to flow on the weaving area. Given our model it can be possible to plan the weaving areas imposing the intersection capacity and given flows on the weaving area. In other words, the dimensioning of the weaving areas is possible by knowing the O/D matrix. Keywords: roundabout, behavioural model, lane changing.

Keywords

roundabout, behavioural model, lane changing.