This isn't a totally new idea.
Shweeb has demonstrated this with human powered devices. I have spend some time thinking about it myself.
But there are many issues, that have not all been solved:
- switching:. How do does one switch tracks? The Mechanical construction has to be fail-safe (Driving into a broken switch at full speed…). Who decides the direction? A central computer or the driver?
- cost: Unless this is supposed to be limited to big cities where cost doesn't matter, it has to use as little material as possible.
- reliability: Currently everyone is responsible for their own car/bike. If one fails, it stops at the side of the road, which usually isn't a problem. Stopping mid-air is a problem, because it brings the all cars on the track to a halt.
- energy: The choice is basically normal fuel (stinks) or high voltage (easy to kill yourself).
- cost of participation. The streets are usable for everyone (cars, motorcycles, bicycles, unicycles, pedestrians). If the whole thing requires to buy a very expensive capsule, or to rent one, I don't think it will find a lot of use.
I do like the idea, but I don't think it solves the problem of big cities. Public transport works really well combined with bicycles.