A great point, but it is perhaps already economically viable on a small scale, if done correctly. Consider a place like Manhattan. Getting around in a car is a

A great point, but it is perhaps already economically viable on a small scale, if done correctly. Consider a place like Manhattan. Getting around in a car is already extremely impractical. Because it's easy to suspend a rail in the air, compared to a traditional road, it could be built right over the existing infrastructure. Population density is high, so you don't have to build very much of it before it becomes convenient. And few people in Manhattan would care that they can't get to rural Texas in their sky-car. Now, if you supply electricity through that rail, it makes the cars much easier and cheaper to make. They would also be much lighter, which means the rail itself doesn't have to be as strong and so can be cheaper to build. And they would be more compact, which means people won't pay as much for a parking space. Can somebody give me half a billion dollars, I have an idea for a startup...