Final answer:
Motorists should stop 15-50 feet from the nearest rail at a railroad crossing, which could translate to roughly 1 to 3 car-lengths, to ensure safety while a train is passing.
Step-by-step explanation:
When approaching a railroad crossing with flashing red lights, ringing bells, descending or lowered gates, or flag signals, a motorist should stop at a safe distance. This distance is typically around 15-50 feet from the nearest rail, though this can vary based on jurisdiction. It is crucial to stop far enough away so that if a train were to pass, your vehicle would not be in the train's path, considering the overhang that might extend beyond the rails.
Vehicles must not go around or under descending gates, or ignore flashing lights, as this would be dangerous and illegal. Always observe and obey the signals at a railroad crossing for the safety of everyone involved. In terms of car-lengths, assuming the average length of a car is about 14 to 18 feet, this would be approximately 1 to 3 car-lengths away from the railroad tracks.