If large infrastructure changes are in the mix, then the self-driving problem is trivially solved using a pair of metal guide rails. They also greatly increase the cargo capacity of the vehicle, a win-win.
There's still a product requirement missing there, which is the ability to get to lots of different places.
I think there's a lot of economic logic in a vehicle that can navigate easily constructed roads - without any smart devices embedded in them - and yet still needs metaphorical guiderails for the exceptions like construction zones and downtown populated areas. That still keeps road construction cheap (just asphalt and paint!) but gets you 100% of the way to where you want to be. If you add rails you need to lay them everywhere that a road is now, and you need switches at each intersection.
