Potential shift from transit to single occupancy vehicle due to adaptation of a high occupancy vehicle lane to a high occupancy toll lane

Abstract

Modifying a high occupancy vehicle (HOV) lane into a high occupancy/toll (HOT) lane generally involves allowing single occupant vehicles (SOVs) to travel on the free-flow HOV lane for a toll. This may entice some former transit riders to pay the toll to obtain the benefits of traveling in their own vehicle on the HOV lane. Thus, the introduction of a HOT lane has the potential to impact transit ridership, dramatically lowering the average vehicle occupancy of the lane. In 2003, surveys were distributed to park-and-ride bus passengers on the Katy Freeway and Northwest Freeway corridors in Houston. Passengers’ responses to questions regarding their trip characteristics, their socioeconomic characteristics, and stated preference scenarios were used to develop a mode choice model. To determine how transit passengers might react to a proposed HOT lane, HOT lane scenarios with varying tolls and travel time savings were simulated using this model. For all scenarios, only a small percentage of transit passengers were estimated to switch to driving alone on the HOV lane. Fewer people would switch during the peak period than during the off-peak period. Transit passengers shifting to SOV on the HOV lane would reduce the average vehicle occupancy (AVO) only about 1 percent to 2 percent. SOV drivers shifting from the general purpose lanes to the HOV lanes are likely to affect AVO much more. However, as long as free-flow conditions are maintained, this analysis shows that the HOV lane can be successfully adapted to a HOT lane and move more people, even if a few transit passengers choose to drive alone.