How to know when off the crossing

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storminorman

New Member
Since I work next to to the rails, I often wonder how do they know when the end of the train has cleared the previous crossing. I'm guessing the 'end of train device' reads something that tells the engineer the end has cleared...but just how does this work? A sensor buried or attached along the rail that does this....or...?
 

5thGenRR

New Member
Since I work next to to the rails, I often wonder how do they know when the end of the train has cleared the previous crossing. I'm guessing the 'end of train device' reads something that tells the engineer the end has cleared...but just how does this work? A sensor buried or attached along the rail that does this....or...?
Are you talking about the Crossing Guards and or lights? I don't work for that side but when I asked that question I was told the locomotives/cars ground out the rail with the wheel sets when they get to the sensor. I have also been told if you put a piece of metal across the rail near the sensor it will actuate them too.
 

roee

Active Member
The engineer knows they are past a specific point by using the counter on the locomotive. If the train is 8600 ft (which they know from their paperwork) then they run the counter and once it reaches 8600 ft, then they have passed the specific spot. But that is more used for speed restrictions.

If you are asking about how the crossing knows a train is clear of the crossing, that's a bit more complicated, and depends on the crossing, but the simple answer is track circuits. The most basic grade crossing protection is a 3 DC track circuit. There is a West Track, Island Track, and East Track. When a train is Westbound it will drop (cause the relay to de-energize) the East Track first, and the crossing will activate. Then the Island Track will drop while the East track is still down, this will set a stick. Then the West Track will drop. Then the East Track will pick up, and then the Island track, causing the crossing to recover (stop activating). Biggest problem with this system is in 79 MPH track you need to set the distance of the track circuits for max speed to get the FRA required 20 seconds warning time. So if a train come at 10 MPH you'll get a very very long warning time. So there are more advanced and complicated Constant Warning Time devices, but I'm not going to get into that here.
 

storminorman

New Member
Counter makes sense to me. I just know that often times a train will slow down and stop and I assume the last car has cleared to last crossing to allow traffic across. I'm even been at that crossing and watched a train slow down, and 'mysteriously' stop just a short distance past the crossing. So, supplied paper work that contains that string of cars total distance and a counter that has to be activated when passing that set point allows 'him' to know he is clear. I Knew there had to be something. Thanks all!
 




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