Fixing Train behavior ?

Good evening, and sorry for my bad english, i try my best 😉 I hope this is the correct place to ask this, if not, i am realy sorry for this. I've been wanting to fix a small issue for a long time, and I've finally decided to take the plunge. I read a lot of things, but there are still a few questions I can't find the answers to. I'd like to solve a problem that a lot of people are talking about regarding train behavior: "why are they not looking for an alternative path if the first path have a red light signal". I'm quite familiar with coding C++ VS.net, pathfinding , I'd like to create something that would allow trains to recalculate their path via alternative routes, taking status changes of traffic lights into account. Unfortunately, I haven't found a way of interacting with trains or their methods of finding the shortest route. If anyone has an idea or a direction in which to look, a documentation a should read, I'd be very grateful. I already installed all the software needed unreal editor etc, i am ready to code 😉 Thanks for your help !!!