I DON’T KNOW IF IT WOULD WORK, BUT REPLACING SUBWAY TRAINS WITH AUTONOMOUS VEHICLES SOUNDS LIKE AN IDEA WORTH EXPLORING

I have written several posts on autonomous vehicles.  I think they will be in widespread use in my lifetime.  
I had never heard this idea before, but it is intriguing: in cities where there are subways, replace the electric trains (an early 20th century technology, at best) with autonomous electric cars.  Such a system would replace the old subway trains with smaller, more efficient, easier to maintain vehicles.  Sounds like it might be a good idea.
I wrote about a superficially similar idea several months ago: have dedicated lanes for autonomous vehicles, like the HOV lane on the freeway.