Grade crossing signals

Grade Crossing Signals are the electronic warning devices for road vehicles at railroad grade crossings.

The basic signal consists of flashing red lights, a crossbuck and a bell, attached to a mast. At most crossings, the signals will activate about 30 seconds before the train arrives.

At crossings where trains travel at 30 miles per hour (48 km/h) or more, there will be a gate added to the signal. The gates will be fully lowered 15 to 20 seconds before the train arrives. The gates will rise or the signals will shut off once the end of the train clears the island circuit.

The time interval may be controlled by a grade crossing predictor, an electronic device which is connected to the rails of a railroad track, and activates the crossing's warning devices (lights, bells, gates, etc.) at a consistent interval prior to the arrival of a train at a grade crossing.

Crossbucks also may have legends saying, for example: "RAIL ROAD CROSSING" (United States), "RAIL WAY CROSSING" (Australia), "PELIGRO FERROCARRIL" (Latin America), or wordless (Canada).

Many states in the US are now requiring the use of this type of equipment at all newly constructed grade crossings.

"Wigwag" was the nickname given to a type of crossing signals once common in North America, named for the pendulum-like motion it used to signal the approach of a train. Albert Hunt, a mechanical engineer at Southern California's Pacific Electric (PE) interurban streetcar railroad, invented it in 1909 for safer railroad grade crossings.

In 1914, utilized alternating electromagnets pulling on an iron armature. A red steel target disc, slightly less than two feet in diameter, serving as a pendulum was attached. A red light in the center of the target illuminated, and with each swing of the target a mechanical gong sounded.

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