Carshare’s emissions and fuel consumption depend on several factors, including the types of trips they are substituting for, how many new trips they generate, and how the vehicles are fueled. User demographics play a key role in determining these factors; for example, if people are primarily joining a carshare to shed their private car or delay purchasing one and thus reduce their overall car trips, then the program may reduce emissions [1]. If, however, users generally come from car-less or car-lite households, joining the carshare program may create more trips than subtract them, and thus may increase emissions. Carshare programs that use electric vehicles, such as BlueLA, reduce tailpipe emissions [2]. Electric carshare programs also expose users to cleaner vehicle types, and carshare users are more likely to later select electric cars when purchasing a vehicle than non-users [2]. However, even zero-emission vehicles generate fine air particulate emissions from tire friction, which worsens local air quality.

Carshares can offer emissions and energy savings by reducing net private automobile travel and by replacing more polluting private fleets with cleaner shared fleets. While some carshare trips replace public transit trips, in aggregate and when taking the life cycle energy and emissions impacts into account, carshares reduce net household greenhouse gas emissions [3]. One study found a majority of surveyed North American carshare users traveled more by car after joining the program, thus increasing emissions, but that those emissions increases were outweighed by emissions saved by users who gave up their personal cars [1]. Studies find that a carshare vehicle tends to replace approximately 15 private vehicles [4], [5]. Carshare vehicles may also be more fuel efficient than the overall private car fleet [6]. Another study, based on the same survey of North American carshare users, found a significant increase in walking, cycling and carpooling among people who joined a carshare [7].

While the market for zero emissions vehicles is growing, zero emission vehicles still exceed the budgets of some low-income potential drivers. Electric carshare programs offer a low-risk way to improve access to clean mobility among car-light or car-free households, without requiring users to pay the full costs of owning and maintaining their own electric vehicle [8].

In disadvantaged communities with especially high rates of air pollution, electric carshare programs may help reduce localized air pollution [9].