However, in order to achieve this, cars will need to be able to either (1) communicate with others in the near vicinity, or (2) be controlled by some central system coordinating the actions off all the cars in a certain area.
I've seen no indication that this kind of communication or central control is necessary. Google has been operating their driverless cars on public roads in real life traffic for (I think) a few years now. I would say any system predicated on central control or mutual communication (beyond what their sensors can show) is both premature optimization and
introduction of unnecessary failure points.
Each car should be self-contained and autonomous, responding to the conditions around it without any illusions that it has any control over or communication with anything else on the road.