> this means that the trip was made easier by car, not that a trip was impossible and is now possible.

If someone chooses to not make a trip then I count it as impossible. I could walk across the North Pole to Europe, but I think everyone would agree when I say the trip is impossible anyway despite that.

> This does not work in populated areas with high demand. (This is incredibly well studied)

You absolute can and I disagree with the studies. Now I will agree that building 50 layers of highway bridges needed is not a reasonable thing to do, but it still a solvable engineering challenge if we wanted to put the money into it.