A difference between passenger rail in the US and high speed rail elsewhere, is US passenger railcars have to meed a high standard for surviving a crash with a freight train. This was enacted because they run on the same tracks, and probably after some horrific crashes.
I think our urban 'Light Rail' can be much lighter because of dedicated routes.
Near my hometown a train hit a tracked manlift that was used to trim trees. Because the lowboy couldnt pass this overpass without getting the bed stuck on the rails, they waited for the train to pass, so there was time to pass the single rail at snail pass, before the next train, because the max speed of this tracked manlift was only 1 kmh
Unfortunately there is a double rail section further down the rail so trains can pass, so a train came in opposed direction before the railway was cleared.
While in previous years the national railways ran a "ape head" train, model year 1964 on this line, with a welded front of sheet metal on structural section ribs, this line was spun off to the private sector, and operated by a company that bought a flimsy train with a glassfiber front. It derailed when hitting the 12 ton manlift, killing the engineer in the process. It was a matter of pure luck that the train was allmost empty at that time.
Here a video of the Dutch NTSB:
When in another village 25 years ago a 15 ton Cat 212B wheeled excavator was hit, the firemen had to cut the engineer from the train because he was slightly pinched, but he lived and fully recovered. The excavator operator however, was dug out from his cab so he could climb out on his own. Needless to say, the Werkspoor train didnt derail, it just had to be towed because the control room was damaged.
Here an image of a Werkspoor "ape head" under construction:
