Car-Sharing: Transportation Solution Or Eco-Hoax‪?‬

In cities across the US, people are hearing of new car-sharing programs that let subscribers drive cars for a few hours at a time. It's promoted as a way to reduce toxins and [CO.sub.2] emissions by allowing drivers to leave their cars at home, take mass transit to work, and rent a car for trips during the day. But is there any evidence that car-sharing actually reduces the number of cars on the road? Or could it be an eco-hoax that generates money for a few car rental companies while actually making environmental problems worse?