California Partners for Advanced Transportation Technology

California law currently allows certain permitted low‐emission vehicles (i.e., hybrids) to use high‐occupancy vehicle (HOV) lanes regardless of the number of occupants. In September of 2006, the maximum number of permits to be issued was raised from 75,000 to 85,000. The Caltrans analysis after the issuance of 50,000 permits concluded that hybrid vehicles were not causing breakdown on California HOV lanes [1]. However, studies of the effects of hybrid single‐occupancy vehicle use on HOV facilities around the nation indicate that California HOV lanes will become congested eventually, especially if Hybrid vehicle permits continue to be issued after the current cap of 85,000 [2]. Therefore, flow sensors coverage must be adequate to monitor increasing congestion, and assess the wisdom of proposed increases in the permit cap. Moreover, the Federal Highway Administration (FHWA) requires that HOV facilities receiving federal funding allow hybrids only if doing so doesn’t degrade the level of service of those facilities. The purpose of this project was to assess the adequacy of Caltrans’ existing detection infrastructure, and to determine the potential costs associated with any needed improvements.