Cars seem fundamentally different than his other examples: Spacecraft, underwater vehicles, and airplanes. The importance difference is cars have a clear, visual grid of where they can travel and where they cannot travel. Painted lines on the road  and navigational signs provide a construct of the environment around them.<p>Maybe the closest comparison is subway &#x2F; metro rails. There are already many fully automated subway systems: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;List_of_automated_urban_metro_subway_systems#Grade_of_Automation_4_Systems" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;List_of_automated_urban_metro_...</a>