This entire concept doesn't make much sense.  Working in a shop is efficient with access to hoists and other tools that would be impractical to take to a driveway or parking lot.  The weather has to be a factor also.  It would make more sense for dealerships and mechanics to offer an option where a driver picks up your car, takes it to the shop, and the returns it when the job is complete.  Use a deck truck to pick up and return the vehicles for maximum efficiency.