Tom disagrees with me:

I think the less parking/more density argument being put forth is a bit optimistic. Obviously self-driving cars would be phased into the fleet on the road slowly. So long as that’s the case, it’s hard to see how self-rearranging, super-dense parking lots can be made to work. We’ll have to wait for the entire fleet to turn over — a process that, given the steadily increasing quality of modern cars, will take longer and longer as we wait for robot cars to arrive. I can see how a car that’s easier to share — or even just one that can drop you off and then go its merry way — could help reduce the amount of parking we need and build. But it doesn’t seem likely to make a significant difference during my lifetime.

The more immediate consequence is this, though: if automated carsharing drives down the cost of taking a trip in a private vehicle (you don’t have to pay for the full upkeep or purchase of the vehicle, or pay for a driver’s time); and if not having to spend time piloting the car drives down the personal cost even further, won’t that encourage more trips in private cars? And won’t that actually encourage suburban settlement patterns?

I think Tom’s being too pessimistic in his first graf. Parking in cities is expensive. Developers know this and the city knows this. As such, developers and the city are increasingly working (with laudable pressure applied by planning organizations) to reduce city parking anyway. So let’s say that minimum parking requirements no longer apply and you’re a condo developer. You know your residents will want some level of automobile access. You can either provide a spot for most or all of the units, at significant expense and opportunity cost. Or you can provide a spot for ten auto-cars and use the rest of the space for more condos. Even better, you can contract with an auto-car company that provides auto-car service to multiple condo buildings and ditch all the parking spots.

The assumption, you see, is not that we’ll all have our own auto-car and super dense parking lots. It’s that many more people will car share because it will be cheaper and easier to use such services. Presumably, there are a lot of urban residents on the margin between owning a car and requiring a parking spot and not owning a car. Make not owning a car easier, thanks to auto-cars, and you push marginal folks away from car ownership.

The other thing to remember is that there’s going to be a critical mass dynamic. For now, it still makes sense for a lot of institutions in the city to make some allowance for people with private cars. Reduce the number of residents with cars by enough, and a point will be reached at which most businesses have no incentive to cater to folks requiring parking.

As for Tom’s second point, well, it’s hard to say. We haven’t seen all that many successful car-sharing services in suburbs yet, so it’s difficult to know how the costs might play out. But the important variable is going to be how such services affect the relative advantage of living in dense urban places, compared with drivable suburban places. In my mind, the biggest costs to urban car ownership (other than ownership itself) are associated with parking. Auto-cars would address that problem directly. In suburbs, the biggest costs to car ownership (other than ownership itself) are associated with congestion. Auto-cars do not directly address this, and while an entire fleet of auto-cars might coordinate to improve traffic flow, it will take some time for the entire fleet to rollover, as Tom notes.

Moreover, the economics of shared auto-cars in suburbs probably won’t be quite as good. Everything is farther apart, which means that to provide convenient service you have to have a lot of cars that are frequently idle, which is bad for profit margins and would make the service more expensive. Otherwise, the time between the summoning of the robot car and its arrival is annoyingly long, which would reduce adoption of the service.

These things would be, basically, cheaper, safer, more convenient taxis. It’s hard to argue that cheaper taxis wouldn’t primarily benefit urban dwellers and urban areas.