Roundabout Capacity: New Perspective

Present roundabout capacity models utilize gap acceptance models or empirical models to determine capacity at approaches to a roundabout. Capacity calculations for a roundabout are determined as the capacity of approaches based on the circulating flow around the roundabout. In this paper we propose a novel approach to analyzing roundabouts. A new performance measure “Maximum Average Flow” is used to determine flows on approaches so as to ensure that there is no gridlock. This paper demonstrates that the maximum number of vehicles that can exit from the roundabout is dependent upon the average trip length and the average maximum flow around the roundabout that can be obtained. A control strategy based on the average flow and average trip length is proposed. The macroscopic properties and the control strategies are tested on one lane and two lane roundabout using microscopic simulation.