You must stop within _________ of the nearest rail at a railroad crossing when you see a lowered crossing gate, a flashing electric signal, a posted STOP sign, a flag person giving you a signal, or a rapidly approaching train.

You must stop within 10 to 50 feet of the nearest rail at a railroad crossing when you see a lowered crossing gate, a flashing electric signal, a posted STOP sign, a flag person giving you a signal, or a rapidly approaching train. (Trains are at least six feet wider than the tracks they run on, so you don't want to get too close.)