Just curious, if the rails are such an issue, is it not just cheaper to drive the cars (no need for self driving?) or is paying someone to do it not worth the complexity savings? Or are there other downsides to not having the rail?
At the other end of the line, outside the tunnel, there's a whole rail yard. The different kinds of cars have to be sorted out, loaded, and unloaded. So there's a need for a big staging area.
Here's an overview of traditional tracked systems.[1] I've tried to find a video of the back end system and yard, but nobody seems to make such videos. It's too boring.
[1] https://www.robbinstbm.com/products/tunnel-boring-machines/b...
[2]
I see what you did there.
tired vehicles
A perhaps very stupid question, but why not make the cars self-driving the way we built self-driving robots from LEGO as kids? That is, line-following cars. It's effectively a virtual track - but I imagine painting a line or building it from cheap plastic would be cheaper than putting actual rail tracks in, and unlike generic driving automation, line-following is an old, well-understood and solved problem.