Capacity Analysis of Signalized Traffic Circles in Comparison with Conventional Intersections

Abstract

Full signalized traffic circles are operating in some countries to serve the heavy turning traffic flows at large-sized road junctions. Their capacities are influenced by many factors, such as the traffic conditions, signal control types and geometric layouts. The objective of this study is to find out the specified traffic demand conditions that signalized traffic circles are preferred in different cases of the number of lanes and lane configurations. A signal optimization model for the traffic circles is proposed for investigating five cases of signalized traffic circles under various traffic demand conditions. The results showed that signalized traffic circles have higher capacity than signalized intersections in some specific cases, e.g. when the total number of approach lanes reaches five or when more than one right-turn lanes are required. Besides, an analysis on the relationship between the capacity and the occupied area is conducted to further consider the geometric influence.