Optimal Setback Planning and Delay Analysisfor HOV Lanes

To maximize the potential for success of an urban high-occupancy vehicle (HOV) lane, there are several design intricacies that require special attention, particularly at critical intersections. This paper is based on extensive research of HOV lanes, specifically their optimal setback planning and the resulting impact on delay, that was conducted recently in Israel. A setback, the termination of an HOV lane prior to a critical intersection—typically characterized by long delays and diverging queues—allows passenger vehicles, in addition to buses, to use the HOV lane. Throughput capacity is thus increased and delay for passenger vehicles reduced at the critical intersection, especially when the HOV lane is not utilized to its fullest capacity. The paper also presents the geometry of a setback, with and without a right-turn lane and, in addition, introduces the development of a model for determining the optimal length of a setback. Average delay to HOV vehicles and to non-HOV vehicles is given as a function of the degree of saturation for a design that both includes and does not include a setback. At critical intersections, the provision of an HOV lane with an optimal setback is shown to result in the least amount of total passenger delay.