Yeah that would be ideal. Sadly a lot of stuff goes wrong in building rail because governments have to do it and clearly suck at it, and if it weren't so, there wouldn't be nearly as many trucks on the road.

Unlike building rail, the concept I outlined would be feasible to do for a private corporation though, even a startup. The delta in necessary resources between the two is huge.

I'm also not quite convinced that you can pack nearly as much cargo on a rail at the same time (with different destinations) as on the road, but the reason for that believe might be the fact that I'm not a rail expert.

Yep.

I don't really see the point in anything long range for autonomous vehicles in the near-term. We should optimize the use-case of them driving people and goods to and from train stations. For this use-case it should be entirely fine if the max speed they can achieve is 20mph. The stopping times and force that can be achieved at those speeds should bring down the danger by quite a bit.

you mean like a .. train