I thought I never had to think about PRT (personal rapid transit vehicles) again because self-driving cars had replaced them in the imagination of "what if mass transit...but it's cars" crowd. But then Elon came along and told everyone he could run PRTs in tunnels (not a new idea) and stupid nerds who don't know anything about transportation got all excited again. The stupidest article every written on such a thing was just published in the Atlantic (you will go have to find it yourselves). As someone remarked, when magazines publish things that are this stupid on things you do know about, it tends to make you doubt whether you can learn anything about the things you don't know about from them. The reason I haven't read The Economist in years.
It's so stupid one can't even try to rebut it, but in general:
1) you can move a lot of people in trains.
2) you can't move a lot of people in small individual/shared vehicles.
3) more potential stops and more flexible routing always slow things down, no matter how clever you think your solution to this problem is.
4) as you think more about these problems, you inevitably pull yourself back to a more fixed route/fewer stop system with larger cars until you converge on...a basic subway system.
