Carsharing is the shared use of a vehicle fleet by members for tripmaking on a per trip basis. There are four forms of carsharing in North America today: 1) roundtrip, 2) one-way, 3) peer-to-peer, and 4) fractional. In roundtrip carsharing, members begin and end a trip at the same vehicle location and typically pay for use by the hour, mile, or both. One-way carsharing enables members, who pay by the minute, to begin and end a trip at different locations—either throughout a free floating zone or stationbased model with designated parking locations. Peer-to-peer carsharing functions much like roundtrip carsharing; however, the vehicle fleet is typically owned/leased by private individuals and facilitated by a third-party operator. Finally, the fractional ownership model enables users to co-own a vehicle and share its costs and use. Roundtrip carsharing has been operating in North America for over 20 years. In July 2015, there were 39 roundtrip carsharing operators in North America with a total membership of 1,005,893 and a collective fleet of 18,582 vehicles. In 2010, one-way carsharing launched in North America in Austin, Texas, with the car2go service. As of July 2015, there were three one-way operators in North America, serving 511,000 members with a collective fleet of 6,870 vehicles (Shaheen and Cohen, 2016, forthcoming).