Comparison of Capacities of High-Occupancy-Vehicle and General Purpose Lanes

Previous studies show that high-occupancy-vehicle (HOV) lanes provide less vehicular capacity than adjacent general purpose (GP) lanes by adopting the traditional single-value freeway capacity concept, while the randomness of capacity of a facility in operation is a well-accepted notion. This paper conducts a systematic study on the capacity of HOV lanes and adjacent GP lanes using both deterministic and stochastic approaches and compares their capacity values under both settings. The capacity reduction of HOV lanes is found to be in the range of 10% to 25% in the deterministic estimates. In the stochastic setting, for any value of the breakdown probability, GP lanes always offer a higher capacity value than the HOV lane. The magnitude of the capacity reduction varies at different breakdown probabilities. At a 15% breakdown probability, the reduction is in the range of 15% to 30%.