> Crashes would be avoided by having every train know about the train ahead and behind, and unable to make any move which would cause a collision (ie. it is not allowed to slam the brakes on if there is a train right behind you).

Note that with any latency in the system, they need to consider not just the train behind, but /several/ trains behind: https://two-wrongs.com/keep-a-safe-following-distance.html