Believe it or not, a lot of driving takes place in heavily driven territory :)
And I'm sure the autonomous vehicle will have a go-very-slowly mode for navigating people's driveways and similar places the mapping cars haven't been yet.
The world is pretty well mapped at this point I don't think this will be a showstopper.
And the nice thing about driver less cars is that they can drive wherever and whenever pretty cheaply. There's no driver to pay. Just the electricity bill for charging the vehicle and some servicing/vehicle depreciation and other fixed cost. That's a race to the bottom in terms of cost.
There's no good economical reason to limit this to just small areas. You might charge passengers a bit extra if they are further out or even for the distance the car has to drive to pick them up. But there's no good reason for that to be very expensive as it would be with a paid driver.
