Cumulative Impacts of Carsharing and Unbundled Parking on Vehicle Ownership and Mode Choice

The provision of sufficient parking for new development in urban areas often is a subject of debate for developers, city agencies, businesses, and the general public, given the differing priorities of each group. The challenge is to create walkable, transit-supportive neighborhoods with minimized parking and traffic impacts that also ensure the marketability of new development. To address that goal, several cities have enacted policies and programs in recent years to encourage carsharing and unbundled parking. Although the independent effects of carsharing and unbundled parking have been studied, research is lacking on the joint effects on parking demand and vehicle use. This paper discusses the findings of a study conducted in 2010 that surveyed residents of 13 buildings in downtown San Francisco, California, to determine any differences between those residents of buildings that provided both carsharing and unbundled parking and those who lived in buildings that offered neither. The differences were examined in terms of vehicle ownership, commute patterns, and carshare vehicle use. San Francisco was selected because of its relatively large number of residential developments that provided on-site carshare vehicles and unbundled parking. These facilities were provided, in part, in response to recent, local ordinances that required new residential and commercial developments to unbundle parking and to host carshare vehicles. The findings of this study suggested that the presence of both carsharing and unbundled parking in residential developments had a significant impact on vehicle ownership and that carshare members had significantly lower levels of vehicle ownership and drive-alone rates than nonmembers did.