Science!
It looks like a brilliant way to avoid a traffic jam, until you imagine hundreds of people with those things. You'd get 3D traffic jams, 3D road rage, and 3D bodily injury.
Driving now, you mostly think about one dimension (speed in a straight line) and occasionally about a second dimension (turn left or right). But with those things, you'd have to constantly think about three dimensions. Are you gonna trust your Fellow Man to do that?