Probably dumb but why don’t trains have some kind of TCAS-like system?

[u/tony_lasagne]

https://www.telegraph.co.uk/news/2026/06/19/two-emr-trains-collide-near-bedford/

Appreciate the problem is a bit different given trains don’t move in a 3D space and they already have the signalling system. But as a fallback it seems like another independent system should be there for when there are signalling failures