Abstract
A roundabout is an alternative type of junction control that reduces delay under low traffic demand. Conditions under which they are advantageous in terms of capacity and delay have been already shown in existing researches. However, the implementation of roundabouts is likely to be negatively evaluated, particularly in Japan; due to safety reasons since traffic conflicts are inevitable when merging. In this paper, a methodology for the performance evaluation of at-grade junctions considering a trading-off relationship between delay and vehicular conflicts is proposed. The performance of signalized intersections and roundabouts are also compared by applying this methodology. As a result, it was found that roundabouts are still more advantageous than signalized intersections when approaching traffic volume is less than 500 vph, even though not only delay but also conflicts were taken into account as evaluation indices.
