What makes a railroad crossing signal go on?

Train crossing signals are worked automatically by electricity made to flow when the train’s wheels touch certain sets of rails near the crossing.  People walking or riding need to be warned at an approaching train when they are about to cross the tacks on the highway.

Railroad Crossing Signal

Safety gates may close.  Electrically operated waving arms and flashing red sights accompanied by the ringing of a crossing bell can also warn of an approaching train.

When you see a train speeding down the track, you may wonder how the signals know it is coming.

The safety signals are operated automatically by an electric current that flows through special sets of rails near the crossing.  When the train’s  metal wheels touch the rails, they close the electric circuit. Causing the safety gate to close, the red lights to flash and the crossing bell to ring.

When the train is safety through the railroad crossing the wheels touch a second set of electrified rails on the other side, which turn the signals off and open the safety gate for the traffic.–Dick Rogers