The current self-driving systems effectively assume that they are in a minority on the roads and that human drivers will use their intuition to understand that the vehicle is automated and take that into account.
A transport system that simply automates a problematic form of transport also inherits all the problems of that mode of transport.
Just a Uber has created more car journeys, it is not clear that driver-less cars either will reduce congestion or the number of journeys that are made by car.
If they lead to an increase in congestion then automated vehicles effectively create an intractable problem for themselves rather than solving current transport problems.