I think concepts like this will REALLY take off when you can do one-way journeys.

At present, the requirement to return to base and pay rental until you DO return is a major flaw.

People are taking charge of a car and parking it up during the day, only getting their money back or the meter to stop ticking when they finally get back to the base station after the full working day.

At least some fraction of those cars can be re-used for business or shopping uses during the work day.

And maybe there would be some value in having a person associated with the car who would move it from one place of demand to another?

Oh hang on - isn't this the thing we call a TA-XI?