At a railroad crossing, you must stop _________ before the railroad tracks.

Explanation

When you approach a railroad crossing, slow down, look for a train, and be ready to stop. If you see a railroad crossing sign, a signal whose red lights are flashing, or a gate that is down, you must stop between 15 and 50 feet from the nearest rail. Trains are at least six feet wider than the tracks they run on, so you don't want to be too close.