How does a railroad crossing gate know that the train is coming? Radio signal? Detector in the tracks?

Question

How does a railroad crossing gate know that the train is coming? Radio signal? Detector in the tracks?

Answer 1

Good question.

Microcurrents in the rail that sense the approach ot train or railroad equipment.

senses not only the approach of the train but the speed so that if a train is coming very slowly they will not activate until the train is close, and if the train stops before the crossing they know and will let the arms back up.

Keep in mind that crossing gates, bells, lights, and whistles are all mechanical devices and can (and will) fail.

Not all crossing protection devices have battery backups and in the event of a power failure there is no guarantee they will work, some do, some dont.

The only way to stay alive is for you to look, do not trust your life to mechanical devices.

No matter how much redundancy is built into a crossing system, it will fail.

Another thing to keep in mind, there is certain railway work equipment that is designed NOT to activate the crossing protection, the wheels are insulated from the axle.

Please look, both ways, every time!!

Answer 2

More than I wanted to know but here you go

http://matt.zont.org/signals/crossings/x...

Answer 3

Think of it this way. The track has electricity in it, on both sides of the crossing, out to a predetermined distance. This electricity is less than a flashlight battery output. When a train enters the track that is electrified for that particular signal, it is actually shorting out the system when the electricity circuit is bridged by the train's wheels and axles. This activates the signals.

Answer 4

When the crossing arm is up, the crossing gate mechanism is turned on.  When a train crosses a certain section of track, approaching the crossing, the wheels of the locomotive short out a circuit from one rail of the track to the other rail.  Relays in a housing that sits near the crossing pick up the signal, and in turn, turns off the crossing gate mechanism, and the arm comes down.  It is turned on when it is up as a safety feature.  If there was a power failure of some type, then the arm would come down across the road even if no train were coming.