The Muller 400 has been around for awhile. It can't fly because it has no wings. Small detail. I've seen versions with tilt rotors, but they always fly on tether and behave badly. I think it's a money pit. I don't see virtual roadways as an impossibility. GPS will play a major role. The big problem is if you need to stay in the air, then you're going to need fuel. You can't fly around with no means of support. These cars look great to the layman, but look closely. The laws of physics aren't forgiving. Even reasonable designs have problems. How do you fly a car with no wings and no rotor?