Railroad crossing false alarm

METRA (Chicago) this morning, about a half hour before the first commuter train of the day, something triggered the railroad crossing signals. The gates went down, the lights flahing, the bells ringing.

So I just watched for the freight train (not particularly unusual on that line). No freight train, no nothing. The gates went back up after a few minutes.

What could cause that?

Thank you.

If it was April, I'd wager it was this: http://agraveinterest.blogspot.com/2013 ... train.html" onclick="window.open(this.href);return false;

I was driving through Julesburg, CO this afternoon.

An eastbound UP freight was pulling out of the yard there, just starting to gather speed.

On a road crossing was a semi truck with a large gravel trailer. For some reason not apparent to me, the track was stopped spanning the tracks.

The engineer was blowing his horn. The truck just sat there. This was on a road that made an intersection with the highway I was on.

As I pulled alongside the lead loco, there was a very loud bang. The engineer had dumped his air to avoid hitting the truck.

The truck driver slowly pulled off the tracks.

I'll bet there were some choice words from the engineer!

Les

Lots of times a train can activate the crossing but then stop short of it. After a few minutes, most crossing gates automatically "time out" if the train hasn't crossed them to allow traffic to flow. When it senses that the train is moving again, it will reactivate the crossing and lower the gates. It is possible that there might have been a train movement of some sorts that activated the crossing but never actually went over it. The crossing could have timed out or the train left in the other direction.

If it was wet outside, it is possible the circuit may have shunted itself due to a lower resistance in the ballast than in dryer conditions.

Is there a siding somewhere near to this crossing?

Lot of things could have caused it to go into detection. Momentary drop below 10/12v pos,neg DC, tuned shunt going bad thereby causing whats known as a 'tail ring'. I've also seen xings fire off when the dispatcher lines a signal, or could be a hyrail trying to get on/off somewhere inside the approaches and his wheels slip off the rails and his axle hits and shunts it out. Like I said, lots of things.

RearOfSignal wrote:Is there a siding somewhere near to this crossing?

Yes.

I am thinking now that is the explanation.

If the switch to the siding is inside the operating limits of the crossing, the gates would come down when the train hits the approach circuit and then they would go up once the switch is lined for the siding. Just a possibility.

Could have been a slight short in the wiring that could have triggered it or Rust build up on the connections. Sometimes if it Rains or if it is vary cold that can have an affect on things as well I remember this being an issue with the older Conrail crossing signals many of which worked off of Batteries stored in a small 3 x 4 foot concrete box a few feet from the tracks. When CSX took over they replaced everything and had some issues with getting the Frequency set the gates would drop down every time a truck driver keyed up on a CB Radio on the near by highway. CSX thought they fixed that problem till they found out the gates would drop when ever a Dispatcher for the county 911 center got on to send orders to the county fire control center. It took CSX about 3 months to get things working the way they were supposed to.