[marvin]

We have a system like this in my hometown, Bergen. I live 50 meters away from two parking garages containing four share cars each. I can reserve any of these at any time via a web app, given that no one have reserved them already.

Payment is $10 per usage plus a surcharge per kilometer driven. Key management is handled either with an electronic card key which checks the current reservation status, or key drop boxes to which all members have access. It's both cheaper and more convenient than owning a car, since I only use a car once per week on average.