Does Car-Sharing Cut Carbon?

Very little:

For the most part, the people who sign up for car-sharing services were barely driving anyway. On average, Americans who use these sharing services see their car ownership numbers drop from 0.47 cars per household down to 0.24 cars per household. In other words, they went from barely owning cars to… barely owning cars. In contrast, car ownership for the country as a whole is about 1.87 vehicles per household. That’s one reason the effect on climate pollution is so small.