You could put the train in a tunnel type segement, then you only really need the lights on the side of the tunnel to follow the way points instead of larger entities, like trees etc, this would also free up some processing speed!
Not sure if you can use the light markers to follow the light entities though, I think Knxrb had mentioned on one of his threads about a flashlight script that followed the player and didnt effect the ambience of the level, but I can't find it right now.
Not sure if this is helpful! but sharing is caring!!