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NYC Transit

NYC’s subway signal system: How it keeps trains from colliding and other things you probably never knew

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  • Perhaps the most important components of the system are its electromechanical relays -- basically, switches -- that are connected to tracks. Upon traversing sections of tracks where relays are located, the devices send signals to the system informing it of where the train is located. Many of today's relays go back to the 1930s. But there are various versions, some more modern than others, and the transit agency is slowly moving toward more modern relays. However, the agency says that because of a
    Photo Credit: Cristian Salazar
  • Back in the 1930s, when the electromechanical relays were installed, the copper cables that were installed to transmit the signals to the traffic lights were insulated with cloth as opposed to modern day cabling that use rubber. Those are still in use today. But water, dust and other elements can cause the cloth to deteriorate.
    Photo Credit: Cristian Salazar
  • Some signal classes are held in a room facing a series of antiquated subway interlocking switch and signal control boards that are still used in the system today. Levers on the control boards operate a fake set of tracks, where students can see how their actions trigger track switches or signals.
    Photo Credit: Cristian Salazar
  • They have the cutest model train at the school! Used to demonstrate and practice the signaling system, the train is somewhat grumpy and takes a bit of encouragement to get running. But watching it go through the traffic signals gives students a chance to see visually how the system actually works. It's like an actually functioning subway train system, just shrunk down to toy size. The model is so cool they should sell it as a kit to make some extra revenue -- the MTA needs all the money it can get.
    Photo Credit: Cristian Salazar
  • Using that cute model train, Habersham showed how a track circuit failure can make it appear as if a red light has been triggered by a train even though one is not even nearby. These phantom trains trigger a red light for the train behind it. To ensure the safety of the train and its passengers, that following train will only proceed at about 10 mph (normal speed is about 35 mph) after getting permission from the rail control center. The track circuit failure inevitably creates a backup of train traffic until dispatch can get someone out to check out what is causing the phantom train. Sometimes, it ends up being nothing more than an aluminum can on the tracks.
    Photo Credit: Cristian Salazar

Like Harry Potter’s Hogwarts, the New York City Transit Signal Training School is hidden away from mere mortal commuters — only an out-of-place working traffic signal marks its beige entrance at the 14th Street and Eighth Avenue subway station.

It is here that the electrical wizards who maintain the critical signal system are trained. That system, which helps operators to detect where subway trains are over the 659 miles of track in the transit network, includes 12,000 signals, 2,600 track switches and 300,000 signal relays. Over an 18-month course, trainees learn how to troubleshoot and replace relays wires, levers and other equipment, much of which dates back to the Great Depression.

Most trainees have some kind of background in electrical engineering or an interest in electrical mechanics. They are the men and women who, if it weren’t for them, trains might crash into each other throughout the city’s subway network.

On a recent tour of the school, amNewYork heard from top officials about how the signal system works and how critical it is to keeping straphangers safe. Here’s what we learned.

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