[Ressuder]

I don't see what the two have to do with each other. Technical reasons aren't why we don't have self-driving trains, it's just that the economy of things becomes very different when your vehicle is about a kilometre or two long compared to maybe 25 metres.

(Yeah, yeah, I know about the kilometre long Australian semi-trailer trucks, but those aren't really practical in most situations...)

[dcposch]

Aussie road trains are at most 55m

(They are still really imposing and impressive, especially at night. On the extremely flat, straight desert roads in the Outback, you can see them miles before they arrive, like a star on the horizon. When they finally get to where you are, they fly by with a hefty gust of wind. They have steel "roo bars" mounted on the front for efficiently generating roadkill. They are loud, brightly lit, and more than half a football field long.)