Cities are valuable in part for the high variety of interactions possible with so many different people. We should figure out how to do fast point-to-point individual transportation for cities. If you live in a city and meet someone interesting, you should be able to be friends with them without one of you having to move.

The US should spend some money researching this possibility. There used to be ideas of moving sidewalks, jet packs, flying cars, etc. These probably won't work but small, high-speed, electric pods in tunnels might.