It is phenomenally simpler to have autonomous driving in an area where the only things on the road are autonomous and there is a standard for interacting cross manufacturer.

Many new cars, and in some countries all new cars (by law), have enough sensors to be made self driving.

Standards are already being worked on. A basic level of autonomy - good enough for an area without human drivers - is being worked on by every car manufacturer. At some point, the vast majority of cars on the road (at least in cities where leasing and turnover s highe) will have the capability to be autonomous.

At that point I expect the car manufacturers to work with the larger cities to make central city areas autonomous only. Software updates will be pushed to all those existing cars, and overnight there will be self-driving on a level which is sustainable.

Once that happens, it will push people to upgrade to newer cars, expanding the number of autonomous-capable cars, and by extension allowing for the expansion of autonomous only areas.

As autonomous becomes more standard and accepted in the public conscious, solutions that will look obvious in hindsight will deal with many areas that we consider fringe now.

I read that Fedex originally claimed there would be areas they would never service. Even if they were right, it is less of a deal than they thought it would be. Same thing will happen with autonomous cars.