Car-sharing is believed to be a solution that can help to reduce both material demand and greenhouse gas emissions caused by cars. The success of car-sharing in achieving these reductions, however, at least partially depends on how car-sharing affects car-ownership and car-use. In this research, we found that car-sharing only causes a reduction in car-use if a significant number of members also give up a car because of car-sharing; therefore, policies should only promote car-sharing while at the same time discouraging car-ownership.
Existing studies have methodological limitations
There have been a number of studies that estimate changes to car-use; however, the vast majority of these studies are based on directly asking car-sharing users how they changed their behaviour. In this study, we estimated the impact of car-sharing on car-use based on a survey of both car-sharing users and non-users in Flanders and Brussels using statistical methods. Additionally, we made a clear distinction between the car-use and car-ownership impacts, and explored the relationship between them. The contributions are thus twofold: first, we outline a new, more robust, method to estimate the impact of car-sharing on car-use; second, we highlight the importance of car-ownership impacts when estimating the overall change in car-use.
For users who give up a car, car-use falls significantly; for those who do not, car-use increases
Based on the sample of surveyed users, between 13% and 69% of car-sharing users had one fewer car because of car-sharing. The average impact of car-sharing on km travelled by car varied from a reduction of 54km per user per week (assuming the largest car-ownership effect), to an increase in 24km per user per week (assuming the smallest car-ownership effect). Therefore, car-sharing may reduce or increase car-use depending on the effect car-sharing has on car-ownership.
This study also highlights the need for more quantitative studies on the impact of car-sharing using more and better data. Such data should include the travel behaviour of both car-sharing users and non-users over time, and could be collected in collaboration with car-sharing firms.
Policies that promote car-sharing should be complemented with policies that discourage car-ownership to ensure less car-use, and lower environmental impacts
If car-sharing only has a small impact on car-ownership, then there is a danger that car-sharing increases car-use, leading to increasing environmental pressures. Therefore, policymakers should be wary of promoting car-sharing without concurrently discouraging car-ownership, and/or car-use in general. Some policy options that could achieve this are outlined below, however further research would be necessary to confirm the feasibility and effectiveness of these, since they were not explicitly part of this research.