"You can’t take 300 million people out of their cars and put them all on mass transit overnight — there aren’t enough seats on the trains and buses."

So you don't use trains and buses right out the 19th Century, you use point to point autonomous EVs. The technology already exists, and modified parking garages could act as bases, so no new infrastructure has to be built. I bet that many companies like Uber and Lyft would love to have a contract to do this in a major city. It's solely a matter of political will that this doesn't happen, and it would be a million times better for the transit user since their stops would always be their front door and exactly where they wanted to go.