[bluGill]

> so you couldn’t run BART trains onto mainline tracks unless you bought heavier (and more expensive) rolling stock than what BART and other metro systems normally buy

That is no longer true. The FRA rules that required heavier rolling stock on mainline rail no longer exists. You will find many people buying trains(and thus should know) who are unaware of this rule change.

You are right about the rest.

[bryananderson]

My understanding (correct me if I’m wrong) is that the 2018 FRA reforms still set a higher crashworthiness standard for mainline stock than fully-separated metro (due to interactions with freight and road traffic), and that this is the case in Europe too. But yeah it’s a huge improvement from the old “rolling bank vault” era, and definitely maddening that many US agencies are still so incurious about improving things! At least Caltrain bought decent-enough modern trains.