Re: Traffic - self-driving vice parked
The big saving will come with ride sharing.
Once the majority are hiring a ride rather than owning a car the scope for a master system organising shared travel can take off - a cross between mass transport and a universal taxi service.
I imagine a system of different sized vehicles for different uses. Mini bus sized pods perhaps powered by super capacitors for local hops, larger/smaller vehicles for group and individual longer journeys.