PERFORMANCE ANALYSIS OF ROUNDABOUTS AS AN ALTERNATIVE FOR INTERSECTION CONTROL IN JAPAN

This study aims at analyzing performance of roundabout as an effective option to other conventional intersections in terms of safety, environmental, space utilization and operational aspects. These aspects are accomplished in several stages. First, various issues related to safety, environment and space utilization are discussed using the past records found in the literature. Second, a comprehensive literature review is carried out on available approaches used in capacity and delay estimations and then suitable formulas are chosen from them so that they can be modified to suite to Japanese conditions. The modifications are done based on a field survey conducted at a five-leg traffic circle located in Nagano prefecture. Consequently, comparison of delays computed at four-leg intersection assuming a signal control and a presence of a roundabout is made. Then, the effective ranges of traffic volume for roundabouts in Japan are identified. As a result, roundabouts are found to offer a good alternative to other intersections under low traffic conditions.