I want to enhance two other ideas I have talked about. The first was the early adoption of self-driving cars for parking. As I noted, long before we will accept these cars on the road we'll be willing to accept automatic parking technology in specially equipped parking lots that lets us get something that's effectively valet parking.
I also wrote about teleoperation of drive-by-wire cars for valet parking as a way to get this even earlier.
Valet parking has a lot of advantages. (I often joke, "I want to be a Valet. They get all the best parking spots" when I see a Valet Parking Only sign.) We've given up to 60% of our real estate to cars, a lot of that to parking. It's not just denser, though. It can make a lot of sense at transportation hubs like airports, where people are carrying things and want to drive right up close with their car and walk right in. This is particularly valuable in my concept of the minimalist airport, where you just drive your car up to the fence at the back of the airport and walk through a security gate at the fence right onto your plane, leaving a valet to move your car somewhere, since you can't keep it at the gate.
But valet parking breaks down if you have to move the cars very far, because the longer it takes to do this, the fewer cars you can handle per valet, and if the flow is imbalanced, you also have to get valets back quickly even if there isn't another car that needs to come back. Valet parking works best of all when you can predict the need for your car a few minutes in advance and signal it from your cell phone. (I stayed at a hotel once with nothing but valet parking. The rooms were far enough from the door, however, that if you called from your room phone, your car was often there when you got to the lobby.)
So I'm now imagining that as cars get more and more drive-by-wire features, that a standardized data connection be created (like a trailer hitch brake connection, but even more standard) so that it's possible to plug in a "valet unit." This means the cars would not have any extra costs, but the parking lots would be able to plug in units to assist in the automated moving of the cars.