A Fancy Hat posted:

Back in the 50s a scientist fed a bunch of metal pellets to a roadrunner, then held a large U-shaped magnet in his hands while wearing roller skates.

There's no reason that we couldn't scale this up and create a clean, efficient, powerful mode of mass transportation for this. We just need to watch out for the rare situation where the roadrunner paints a tunnel on a wall and we crash into it.