You must always stop __________ from the nearest rail of a railroad crossing if a train is approaching.

Explanation

You must always stop between 15 and 50 feet from the nearest rail of a railroad crossing if a train is approaching. (Trains are at least six feet wider than the tracks they run on, so you don't want to be too close.) Indications that a train is approaching may include flashing signals, lowered crossing gates, or the sound of the horn of the approaching train.