Anytime you're stopped, for any reason, you should be in the habit of checking your rear view mirror (if possible) so you can see if the car behind you is not stopping.

Keep your foot on the brake all the time you're stopped; if you see a car approaching from the rear, pump the brakes to alert him to the fact that you're not moving.

And if possible (especially at a RR X-ing) try to stop far enough back so that a rear-end collision won't push you into the path of the train. (I was taught that, when stopping behind another car at a red light, you should always be able to see the road between you and the car in front, for that very reason.)

I have, on one occasion, been forced to run a yellow light after I'd stopped, because I was convinced the car behind me was not going to be able to stop in time. I figured it was either move forward into the intersection or stay there and get rear-ended. If the light had been red, I probably would have taken the hit, but as it was yellow, I took what I perceived to be the better chance. I don't think I would have been able to react in time if I hadn't been anticipating the driver behind me not stopping.

I'm also one of those annoying drivers who slow down if I think the car behind me is too close. <img src="/images/graemlins/wink.gif" alt="" />