Policy Implications of Incorporating Hybrid Vehicles into High-Occupancy Vehicle Lanes

High-occupancy vehicle (HOV) lanes have been regarded as a cost-effective and environmental friendly option to help move people along congested routes. In spite of wide adaptation of policies, the effectiveness of HOV systems has been criticized for its under-utilization. A California statewide policy that allows hybrid vehicles to use HOV lanes was adopted under the expectation that vehicular emissions would be reduced by encouraging drivers to use fuel efficient vehicles as well traffic congestion would be eased through the more efficient use of the reserved capacity on the HOV lanes.

To test the validity of this expectation, the impacts of the policy on the freeway network in Orange County, California was investigated using a method that combines a traditional planning model for demand estimation and analysis with a calibrated microscopic simulation model for accurate measures of system performance.

The policy was analyzed in terms of overall system performance, corridor level performance and air quality. The key findings from this study are that the policy can be expected to have significant negative impact on HOV lanes that do not have reserve capacity. The maximum number of hybrid vehicles that the Orange County HOV system can absorb without significant degradation is about 50,000, and within this limitation, the policy can be expected to be successful in reducing emissions by allowing hybrid vehicles into HOV lanes.