I think this is ahistorical. Flying cars were always point to point "Jetson's" style vehicles, where you didn't HAVE a highway, because everyone just traveled as the crow flies.

It's only when this was obviously impossible that futurists pushed the "mostly a car but can also fly sometimes" angle.

> A helicopter can't go from flying to transport you in a highway

Yes and no. In some EU countries, helicopters accepted to land near highway, and pick up (or disembark) passengers just like ordinary taxi. Also there very typical case, helicopter landed near Gas station to refuel.

Generally, strict restrictions exists on flights over large cities, but over rural area and over big water, regulations easier. Even so, if in large city exists big river, aviation could flighting over it with very easy restrictions.

People's imagination is dumb. They picture cars ,the annoyance of being stuck in traffic, see all the empty sky and think, hmm, you know what would fix this, flying cars. But imagine that world, with millions of flying cars, and it'd be 10 times as awful.

Yeah, something like the (even more) heavily modified DeLorean Doc Brown returned with from 2015. Key technologies still missing would be (a) the energy source (a "Mr. Fusion" which can generate energy from random garbage you throw into it) and (b) some kind of levitation not based on rotors, rockets or jet engines (anti-gravity?), apparently also used in the hoverboards.