I think the best way to do it would be to have like an indestructable invisible tunnel around the train, which can't deform and you cant move it. Then the train doesn't have to have collisions as you simply aren't allowed to crash into the train or cross the tracks.
But, but ... that would spoil whole point of having a train in a first place Could it just have normal wheels that look like a train wheels, then have slidenode rail at center of tracks that train's slidenode connects to, it would then appear to be a train that appears to run on tracks, but really it would run on wheels that have invisible road or something like that.
It would not be better made the train run on the track? I mean, made the train instead of have rims whit tires in the game logic, only have rims? Yeah, I know, It will made rerailing harder, but you can desing a part of the world whit rerailing purposes and then make it look not to obvious for the sake of realism... I want to see what can happen if a train overloads a bridge o runs to fast in a corner... And most important [ MULTI TRACK DORIFTO ]