A study out of the University of California Transportation Center found that car sharing leads to reduced car ownership, preventing the addition of new cars on to the road and maintaining levels of greenhouse gases.

The study surveyed more than 6,000 households that were part of car sharing networks. Prior to joining the car sharing systems, 2,968 out of 6,281 households owned private vehicles. Upon joining car sharing, that number dropped to 1,507 households with cars—a 50 percent decrease.

The study, “The Impact of Carsharing on Household Vehicle Ownership,” is the newest piece of evidence on how car sharing is transforming transportation in cities. “Carsharing can reduce household vehicle ownership because the service can eliminate the need for a private vehicle to complete non-work trips,” the study explains. “In this way, carsharing provides members with an automobile only when needed.” The study further adds that “the shared vehicles eliminate upfront ownership costs, but members still maintain auto access while leading a less car-dependent lifestyle.”

Most notably, the authors explain that the results signify a major shift of car-owning households towards becoming car-less upon joining a car share system. “80 percent of the sample owned no vehicle after joining carsharing,” the study explains. “Most of this shift was the result of one-car households becoming no-car households.”

Besides encouraging families to become car-less, car share programs also deter car-less household from acquiring vehicles. “62 percent of households joining carsharing owned no vehicle when they joined, while 31 percent of households owned one vehicle,” the study explains. “That is, some carsharing members who consider buying a car ultimately decide against it and use carsharing instead.”

The authors also make the case for car share systems improving fuel efficiency:

Advocates for carsharing have frequently argued that the service not only reduces vehicle ownership, but also improves fuel efficiency, because carshare vehicles tend to be more fuel efficient than the average vehicle. While sensible, to date these claims have been hard to evaluate because data have been difficult to acquire. We conducted a survey to evaluate these claims and found strong evidence to support them.

We previously wrote about ZipCar’s role in improving sustainable transportation and reducing private vehicle ownership, all in addition to decreasing the vehicle miles traveled.

Methodology

In order to measure the impact of car sharing services, the researchers conducted online surveys of North American car sharing members. They reached out to the members of AutoShare, City CarShare, CityWheels, Community CarShare of Bellingham, CommunAuto, Community Car, Co-opeartive Auto Network, IGo, PhillyCarShare, VrtuCar, and Zipcar. They asked participants about their travel behavior prior to joining carshare, their present behavior and the number of private vehicles that belong to the household. The authors explain their methodology:

We asked about households, rather than individuals, because carsharing can affect the travel patterns of multiple people in the same household, even if only one person in the household is a carshare member. For example, a married couple may commute to jobs in separate locations, both by automobile. The husband then joins carsharing and starts to commute by public transit, but the couple keeps “his” car because it is newer. They shed the wife’s vehicle and she uses the remaining car for her commute once they become a one-car household. In this case, surveying at the individual level might wrongly suggest that carsharing had not resulted in a vehicle reduction. Surveying at the household level helps avoid this problem.

Download the full study here.