That would be worst-case - if the car went all the way back to where it came from. We could easily be more efficient - garages at a moderate distance with much

That would be worst-case - if the car went all the way back to where it came from. We could easily be more efficient - garages at a moderate distance with much high density (no need of human access) and routing could be optimized to avoid congestion both on the road and parked. But the big win would be with car sharing.