Dynamic Four-Step Planning Model of Empty Repositioning Trips for Personal Autonomous Vehicles

Autonomous vehicles (AVs) offer new technologies that could revolutionize travel, such as greater link capacity and innovative intersection controls. One such traveler behavior is the potential for empty repositioning trips, in which a vehicle travels without any passengers. Repositioning trips could allow travelers to avoid parking costs or make their vehicle available to other household members. However, empty repositioning trips increase the demand for personal vehicle travel. A previous study using static traffic assignment on home-to-work trips showed that repositioning trips still resulted in a net increase in congestion even when link capacity improvements for AVs were modeled. This raises the question of whether empty repositioning trips should be permitted. However, a key characteristic of repositioning trips is that they depart after the traveler has been dropped off. This could reduce the concentration of demand at any point in time. By using dynamic traffic assignment with a more realistic model of link flow on the downtown Austin network, we showed that when repositioning trips encourage travelers to switch to AVs, the resulting improvement from those AVs could decrease congestion. Furthermore, even if all vehicles are AVs, the congestion resulting from empty repositioning is still less than current conditions. Therefore, allowing empty repositioning trips could be beneficial for the traffic network.