Event trigger/train detector

I have an idea where I want to automate a train stopping at a level crossing using the 9v system and PFs. Train passes a mechanical lever which activates a PF switch The PF switch activates the level crossing gates and 2 rail switch tracks on the start/end points of a siding. This isolates the siding so there is no power, and if timed right the train will stop before the crossing. After a duration in which the level crossing mechanism finishes, a delay mechanism will reactive the PF switch...