Traffic Characteristics of High-Occupancy Vehicle (HOV) Lanes

Abstract

Traffic characteristics intrinsic in contiguous and buffer-separated High-Occupancy Vehicle (HOV) facilities are explored by examining flow-density-speed relations with respect to intervening effect from the adjacent general purpose (GP) lane. Detector data are collected from multiple locations and systematically filtered to form well-defined relations among flow, density and speed of the HOV lane that characterize traffic stream in that lane. Analysis of the collected data exhibits different patterns of flow-density-speed relations for contiguous and buffer-separated HOV lanes. The relations in the contiguous HOV lane are distinctively defined as a function of the adjacent GP-lane speed while those in the buffer-separated HOV lane are rather independent of the adjacent GP-lane speed. Implications are drawn for capacity and speed estimates of HOV lanes and documented in this paper. These findings are confirmed by comparative analysis of pre- and post-conversion of HOV configurations (from buffer-separated to contiguous) in a real freeway site.