Based in my knowledge as a public transportation enthusiastist in China, I got really surprised to see a IT problem bring the entire system down. There should u

Based in my knowledge as a public transportation enthusiastist in China, I got really surprised to see a IT problem bring the entire system down. There should usually be some "more manual" backup mechanism that allows downgrade and operation of trains without computerized signaling system. By kinds of token signaling it will still be possible to run trains as long as the physical infrastructure is still there. The efficiency will be much lower and more prone to (potentialy deadly) errors, but no more trains today sounds unlikely.