Cars Driving Through Signal Crossing.

I'm having a problem when trying to place down a signal crossing for a road to stop traffic when a train comes.
Seems like no matter what I do the cars just keep driving through the crossing and drive right through the train, ignoring the crossing completely.
Does anyone have an idea of what could be causing this?
Currently I'm stumped.

Seems like no matter what I do the cars just keep driving through the crossing and drive right through the train, ignoring the crossing completely.
Does anyone have an idea of what could be causing this?
Currently I'm stumped.
