Abstract
High-Occupancy Vehicle (HOV) lanes have been regarded as a cost-effective and environmentally friendly option to help move people along congested routes in metropolitan areas. HOV lanes can be categorized as continuous-access and limited-access based on accessibility. This paper focused on the comparison of the operational performance of four study sites in which conversion of HOV lanes from limited-access to continuous-access has taken place. This paper proposed a traffic flow fundamental diagram based approach in which a statistical approach was applied to estimate the traffic flow fundamental diagram parameters, including free-flow speed, critical volume, critical volume and shockwave speed, for the study. The general-purpose lanes’ traffic flow fundamental diagram parameters before and after the conversion were further used to evaluate the performance of the HOV lane conversion. Results show that (1) the HOV lane conversion leads to a faster shockwave speed on general-purpose lanes during the traffic congestion and thus a freeway with continuous-access HOV lane would see congestion clear faster; (2) the performance of the critical volume and critical occupancy after conversion is site-specific and influenced by the local geometric attributes and associated traffic patterns