killer in an accident
One of the problems with something like a compressed air car is similar to the problems you have with ideas like massive spinning flywheels to recover energy while braking - what happens when you get into an accident?
Let's say you fill some carbon-fiber tanks with enough very high pressure air to power this vehicle up to 100km. Five miles out onto the road you get rear-ended hard and burst the air tank.
Well, we've all seen the videos of dry ice bombs made in soft drink bottles, haven't we? Magnify that effect by hundreds of times and put it a few feet away from passengers and drivers in a car accident, and you've got an awful mess.
So, Pintos used to burst into flames from time to time when hit in the rear. And this new air car? It just blows the car and everyone in it into a billion pieces.
I'm skeptical.