App-based ridehailing services such as Uber and Lyft have revolutionized urban travel. These services improve mobility and reduce demand for parking, but also increase vehicle travel and shift some trips away from walking and public transit.1 As a result, ridehailing has been the largest contributor to increased congestion in recent years in cities such as San Francisco.2 Ridehil services could also be contributing to traffic congestion and pollution when vehicles are out of service between paid rides. Drivers might cruise (circle around while waiting for the next paid ride) or reposition (move to another location in anticipation of the next ride request), both of which can exacerbate congestion and pollution. They might also park (either on- or off-street), which would reduce congestion and pollution but may affect parking and curbspace availability or interfere with other street activities such as drop-offs and deliveries. To gain a better understanding of ridehail driver behavior between paid rides, UC researchers evaluated over 5.3 million ridehail trips in San Francisco in November and December 2016. Each trip was divided into cruising, repositioning, and parking segments
