.. the front/coupler hatch should be designed such that when tilted up upon coupling, the fairing parts should not be stowed away into the train, but remain above and around the coupler such that they prevent adventurous people from trying to reach the other side by crossing over the coupler, which obviously happens now and then, especially in a light rail scenario (i.e. because people don't want to go around the train/wail till it leaves), see here:
http://frankfurter-nahverkehrsforum.de/thread.php?threadid=1...
(see contribution by user "Combino" towards end of page etc.)
So you might use something along the lines of "step-over/climb-over guard".