[sonofgod]

I agree.

In two dimensions, a vehicle moving North-South and a vehicle moving East-West have to cross into each other's path at some point, and 2.5D solutions (bridges and flyovers) help but require significant investment in resources that simply isn't possible at every junction.

In three dimensions, this simply isn't the case; we can separate different directions of traffic by height, and provision of dedicated corridors for changing route is merely a matter of making regulation rather than infrastructure.

There's a reason why we've had autopilot on planes for significantly longer than on cars.

[falcolas]

The flip side is twofold - to take advantage of said autopilot, you need a pilot’s license, which is significantly harder and more expensive to get than a car license.

Aircraft are also expensive (and come with expensive operating costs like airframe examinations), since their failure mode is a more-or-less controlled “falling out of the sky” - so you want the most resilient parts you can have to skew more towards the “more controlled” end of the spectrum.

There’s also a whole network of human traffic controllers who work 24x7 to accommodate our existing air traffic; more would be required.