We all know that a train stops in front of a pole to wait for the pole to lift. But when two trains arrive in front of the pole one after another, they will show a collision, so even if the pole is lifted, neither train will pass. According to common sense, if two trains have reached the front of the pole without colliding at the crossing, they should actually queue up one after another, waiting for the pole to lift and move forward in sequence without colliding. I think this is a bug :(