Wikipedia isn't too bad on this: https://en.wikipedia.org/wiki/Category:Train_protection_systems https://en.wikipedia.org/wiki/Category:Train_protection_syst...

Wikipedia isn't too bad on this: https://en.wikipedia.org/wiki/Category:Train_protection_systems https://en.wikipedia.org/wiki/Category:Train_protection_syst... - and see my reply elsewhere on this page: https://news.ycombinator.com/item?id=9631443 https://news.ycombinator.com/item?id=9631443 I would expect there to be a few real experts on HN, though. (I'm not one.)