Previous research efforts have quantified the capacity of non-barrier separated HOV lanes. However, the majority of these efforts have focused on HOV lanes that usually operate well below capacity. Atlanta's I-85 HOV lanes usually operate under constrained flow conditions during morning and afternoon peak periods. This provides an opportunity to assess the relative performance of the HOV lane to the adjacent general purpose lanes that also undergo constrained flow conditions. This paper examines the relationship between the performance of the HOV lane and the adjacent general purpose lanes, examining speed differential effects as a function of congestion on general purpose lanes. The research provides evidence of a sympathetic reduction in vehicle speeds on the HOV lane. This is likely explained by the safety concerns of the HOV drivers associated with the potential for vehicles using the congested general purpose lanes to jump into the HOV lane, as well as the safety concerns of HOV drivers looking for an acceptable gap to merge into the GP lanes in order to access a downstream exit ramp.
Abstract