Elon Musk seems to have a particular version of a progressive vision of the future that accomplishes environmental sustainability without requiring people to make any real lifestyle changes. After all, his solution to the environmental unfriendliness of cars is more environmentally friendly cars (Tesla), not other modes of transport that are more efficient per passenger.

So, the cynical take: of course he's going to back a high-speed transportation option that still assumes cars and driving everywhere, rather than one that potentially obviates the need for them by taking people directly from high-density center to high-density center.