What happens if the 'rail' was actually a specific, demarcated line that autonomous self-driving cars used on specifically selected roads that augmented existing public transportation options? That would alert human drivers/pedestrians/bicyclists to be a bit more careful - similar to the brightly colored green lanes that are starting to be provided for bicyclists.
Similarly for long haul trucking applications - could the far left lane/carpool lane be safely dedicated to autonomous trucks during the hours of midnight-3AM with some bright blinking signs paid for by the autonomous trucking industry trade group?
This. I think this is the correct solution, with the self driving cars refusing to self drive on roads that don't have this infrastructure. I actually wonder how much money it would take to cover, say 95% of roads in the US with some kind of "smart paint" that can be detected in rain, through snow, and when covered in dirt or gravel, vs the amount of money spent on developing the lidar.
Was gonna post almost the same idea. You don't need a true "rail" to keep an autonomous car from mowing over people. You need something that's pretty binary "am I on my pre-approved area or not". A special kind of paint or something very low-tech could be the solution.
There will still be the last-mile problem. Even if the "rail" is just cheap paint, you'll almost definitely never have 100% of roads painted, and paint wears over time or gets buried under snow etc.
Eventually we're looking for ways to add "more 9s" to the reliability and safety. A non-rail rail could add a bunch of 9s to well-trafficked routes.
Similarly for long haul trucking applications - could the far left lane/carpool lane be safely dedicated to autonomous trucks during the hours of midnight-3AM with some bright blinking signs paid for by the autonomous trucking industry trade group?