Railroad crossing signals mean that there is a railroad track ahead and that one should look out for the possibility of an approaching train. This signal normally is denoted by a stop sign, the sign "X" or the letters "RR" painted on the street just before the crossing.
Flashing red lights indicate an approaching train, for which a person is required to stop. Other signals that should prompt a person to stop include the horn or bell of an incoming train, a person warning of an approaching train or the sight of a forthcoming train. A full stop is necessary under this signal, and a person should only proceed when a train completes passing through the tracks or when there is no train passing on the tracks.