You are approaching a railroad crossing. If flashing lights, lowered gates, or other signals are warning that a train is approaching, you must stop ________ from the tracks.

Explanation

At a railroad crossing, if flashing lights, lowered gates, or other signals are warning that a train is approaching, 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.