Grade crossing activation at station abutting a road

[MattW]

I know there are several commuter stations scattered around the country that "abut" a public roadway with active grade crossing system. The Beaumont station on METRA is a good example of what I'm talking about: http://maps.google.com/maps?q=pasadena,+ca&oe=utf-8&client=firefox-a&ie=UTF8&hq=&hnear=Pasadena,+Los+Angeles,+California&gl=us&ll=41.795482,-88.037441&spn=0.001602,0.004128&t=h&z=19

How are the grade crossings timed for this situation? When a stopping train approaches, do the gates still go down, or does the circuitry detect the deceleration, know it's enough to stop before the crossing, and keep the gates up? Or do they always activate?

What about while the train is in station? Given that dwell times may be as low as 30 seconds (right?) do the gates go up once the train has stopped if it's not blocking the road, or do they remain down for the duration of the stop? If they do go back up, how are they reactivated?

Thanks,

Matt

 

[ACVitale]

While not familiar with the ones referenced. There are some in South Florida. They typically go down as the train approaches from either direction. They will remain down for approx 1-2 mins. If the train has not started moving they will go back up. When the train starts moving again it blows horns and rings the bells as it approaches the grade crossing. Just before (and I mean a couple feet) the train triggers another sensor and they go back down. (Sometimes the train waits for them to fully close and proceeds but, if all traffic is stopped and they are not fully down I have seen them proceed thru.)

Does that help?

 

[trainman74]

Every morning on my commute, I pass through a grade crossing that's about 2000 feet west of the Burbank-Bob Hope Airport Amtrak/Metrolink station, and it's just as ACVitale describes: a westbound train will activate the gates in advance of the station, but then the gates will go back up within about a minute while the train is stopped at the station. When the train starts to move, they go down again. (Since the distance is 2000 feet, they're always fully down by the time the train goes through after stopping.)

In fact, I can tell I'm a little later to work than usual if I get stopped at the gates because Metrolink Ventura County Line train 101 is stopped at the station (7:11 A.M.). Under normal circumstances, I pass it in the opposite direction as it's slowing down for the station, while I'm on the street that parallels the tracks.

 

[Ryan]

I thought that this thread was going to be about trains that blocked grade crossings while stopped at a station, and was prepared to admit to my (juvenile to be sure) glee at watching the cars lined up while the train was stopped. Most egregious was the car in RGH that was stopped at the grade crossing just barely blocked by the last coach - from the ground, while I wandered about on our 40 minute stop (we were running early).

 

[DET63]

At MTZ, for the eastbound Capitol Corridor and San Joaquin trains, the gates on Ferry Street will usually come down as the train approaches the station, but go back up once the train stops, going down again once the train resumes its trip. For the much longer Coast Starlight and California Zephyr, the gates stay down while the train is dwelling in the station, as either one will be long enough to occupy the crossing.

For westbound trains (southbound CS), the Berrellessa Street gates will come down as the train approaches and passes the station, but I believe they go up even when the CS or CZ is stopped, as the station is a bit closer to Ferry Street, which will be blocked by the CS and CZ while dwelling in the station. (Given that the CZ is only discharging passengers, however, its wait should be relatively short.)

Both of the streets are dead-ends, so there is no other way out if the train is blocking you in.

 

[Devil's Advocate]

At SAS the signals light up and the gates drop during approach but then rise quickly once the train ceases movement. If the trains start moving again then the whole cycle repeats. Next time you should ask what would happen if a locomotive suddenly materialized along the crossing in a big puff of smoke. Or maybe ask what would happen if a sneaky engineer stopped as close as possible to the crossing and waited for the signal to clear before gunning it and trying to foul the crossing before the gates had time to lower.

 

[AlanB]

As some have noted, in some cases the gates come and then go back up with no movement and then the train needs to start moving again to get them to come down.

However, in many cases it's actually not the movement of the train that triggers the gates to lower again; it's a radio signal. If you happen to have a scanner tunned to the correct frequency, you'll hear what sounds a lot like a touch tone phone dialing on a speaker phone. That's the engineer entering a code picked up by a transmitter at the crossing control box. The correct code will order the electronics in the crossing box to lower the gates for the train.

If you encounter a train & station where the passenger service is the only service, then some times the sensors will be set just past the platform. That means that the gates won't come down prior to the train making its stop. They'll only come down after the train starts to leave the station. But this method of course only works on a closed system where there is no freight service and all passenger trains will make that stop. If express trains are scheduled to run on that line and skip that stop, then of course that method cannot be used.

 

[Tracktwentynine]

There are different ways of doing this. I know the "old-fashioned" method in a lot of cases is the crossing gates have 3 sensors for trains.

One is a sensor that stretches through the crossing and a little distance on either side. Whenever this sensor detects the presence of a train, the crossing signals are activated. The other 2 sensors are placed further away from the crossing on either side. These are on a timer, so they activate the crossing for a set amount of time when they detect a train. After that time, the crossing is deactivated, unless the train is still occupying the central sensor (the one at the crossing).

So, for example, lets assume a train is approaching Main Street from the west. When it passes the western outer sensor, the crossing is activated (for let's say, 30 seconds). After 20 seconds, the head of the train passes the central sensor and occupies the crossing. 10 seconds later, the western sensor times out, but the gates stay down because the crossing sensor is occupied. 10 seconds later (20 seconds after entering the crossing), the train trips the eastern outer sensor, which also times out after 30 seconds, either while the train is still occupying the crossing sensor or after it has cleared it. If the train has already cleared the crossing, the gates come up after the eastern sensor times out. If the train is still occupying the crossing when the eastern sensor times out, the gates will come up as soon as the train clears the crossing sensor.

In places where there are frequent trains, and especially if there are lots of passenger trains making station stops in the area, railroads will use more advanced systems.

Charlotte's light rail is a perfect example. It operates like a train for its entire length, activating crossing gates. It's not like some light rail systems that pretend to be a bus downtown (looking at you, Baltimore). When the train is approaching a station on the far side of the crossing, the gates activate as the train approaches and then clear once the train arrives at the station. When the train is approaching a station on the near side of a crossing, the gates don't activate until the train has been at the station for a set amount of time.

Train operators know that the crossing gates have been activated by a pulsing lunar signal that faces them. As the train approaches a crossing, a lunar (white) signal starts flashing as the crossing signals are activated. Once the gates are down, the lunar signal goes solid, meaning that the train can occupy the crossing. For cases when the station is on the near side, the flashing lunar signal is the operators' signal to close the doors and to prepare to depart.