The impact of HOT lanes on carpools

This research investigated the change in carpooling on U.S. roadways once high occupancy/toll (HOT) lanes began on those roadways. HOT lanes generally allow carpools to travel on the lane for free while charging a toll for single occupant vehicles (SOVs) to use the lane. In most cases these lanes were previously high occupancy vehicle (HOV) lanes where carpools traveled for free and SOVs were not allowed. Note that clean fueled SOVs were allowed in some cases. Thus carpoolers could now switch to being a SOV and still access the benefits of the HOT lane – for a toll. This may cause some carpools to break up and become SOVs, thus adding to the amount of traffic and emissions on the roadway.