We're at the point where we could easily fit so large a fraction of the rail length covered/overshadowed by the train with https://en.wikipedia.org/wiki/Track_b

We're at the point where we could easily fit so large a fraction of the rail length covered/overshadowed by the train with https://en.wikipedia.org/wiki/Track_brake https://en.wikipedia.org/wiki/Track_brake that we could pull around 4 G deceleration if we cover the bottom in that brake chains (chain strong; chain flexy enough to just wiggle over humps in the track).