Capacity Modeling of Weaving Areas on Urban Expressways with Exclusive Bus Lanes Based on Gap Acceptance Theory

Intense lane-changing maneuvers at weaving sections often cause traffic turbulence on expressways, especially in the presence of a concurrent medium exclusive bus lane (XBL) and general purpose lanes. Such intense lane-changing activity usually affects the operation and reduces the capacity of weaving sections in relation to their equivalent basic expressway segments. In this context, a study on the capacity model of weaving areas on an expressway with a median XBL is conducted based on the analysis of lane-change behaviors using gap acceptance theory. Two weaving sections on expressways with median XBL are selected as case studies to obtain the estimated capacity as well as the maximum traffic throughput under a certain bus saturation on the XBL. The results show that estimated capacity is larger than maximum traffic throughput because of low utilization rate of buses on the XBL, and capacity is significantly affected by weaving demand. Error measures based on the estimated and observed maximum traffic throughput are analyzed to verify the validity of the proposed model. A sensitivity analysis shows that, compared with the increase of on-ramp bus flow ratio, the increase of off-ramp bus flow ratio results in a more obvious trend of the reduction of capacity and maximum traffic throughput