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.