Grade crossings next to stations -- how do they work?

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Grade crossings next to stations -- how do they work?

Postby jersey_emt » Wed Nov 02, 2016 6:11 pm

When there is a grade crossing near a station stop, like commonly found on the lower Coast Line, how are the lights and gates controlled? The gates go down when a train approaches, and if the train does not stop at the station, the gates work like any other grade crossing and go up after the train is clear. But if the train makes a stop at the station, the gates will raise after the train stops (even though it is within the track circuit controlling the gates), then go back down when the train starts moving again. But how does this work?
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Re: Grade crossings next to stations -- how do they work?

Postby Backshophoss » Wed Nov 02, 2016 8:05 pm

There're 2 methods,1. a control push button in a locked case,used by train crew member,to drop the gates back down.
2. Not sure if NJT has this: Using a DTMF tone(4 digit code) to drop the gates down,done by the Engineer in the Cab via the radio.
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Re: Grade crossings next to stations -- how do they work?

Postby DutchRailnut » Wed Nov 02, 2016 8:35 pm

or a crossing predictor, it measures movement of train in approach block to island circuit,

From wikipedia: predictor, this method required that the crossing be designed to accommodate a train approaching at the track speed limit, which leads to longer warning times for trains approaching the crossing at lower speeds. Very slow trains could have many minutes of warning time, thus delaying highway traffic unnecessarily.

All grade crossing predictors rely on the changes in the electrical characteristics of the rails that occur as a train approaches the point at which the predictor is connected to the rails (the feedpoint). A railroad track occupied by a train or other electrical shunt can be viewed as a single-turn inductor shaped like a hairpin. As the train approaches the feedpoint, the area enclosed by the inductor diminishes, thus reducing the inductance.[3]

This inductance can be measured by connecting a constant-current alternating current source to the rails, and measuring the voltage which results. By Ohm's Law, the voltage measured will be proportional to the impedance. The absolute magnitude of this voltage and its rate of change can then be used to compute the amount of time remaining before the train arrives at the crossing, assuming it is running at a constant speed.

The crossing's warning devices are activated as soon as the computed time until the train reaches the crossing reaches some programmed threshold. The earliest grade crossing predictors used analog computers to perform this calculation, but modern equipment uses digital microprocessors.
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Re: Grade crossings next to stations -- how do they work?

Postby GSC » Mon Nov 07, 2016 1:00 pm

Put simply, the gates "time out". This is a very common occurrence at the Corlies Ave. Route 33 crossing in Neptune. The westbound train pulls into the Asbury Park station and the gates are already down, assuming the train isn't stopping. And now, the interlocked traffic signal at Corlies and Memorial Drive has turned everything into an "all stop" situation, and motorists are getting antsy, and the gates go up. But if the train starts moving again, the gates come down again, after maybe three cars get to cross the rails.

Rt 33 / Corlies Ave. is a very busy road, especially during rush hours and horrible during the summer, traffic backed up sometimes to Route 35 due to those gates.
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Re: Grade crossings next to stations

Postby timz » Mon Nov 28, 2016 6:26 pm

On the Peninsula, Caltrain trains blow the whistle when ready to go, and a microphone brings the gates back down.
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Re: Grade crossings next to stations -- how do they work?

Postby michaelk » Fri Mar 03, 2017 9:48 pm

GSC wrote:Put simply, the gates "time out". This is a very common occurrence at the Corlies Ave. Route 33 crossing in Neptune. The westbound train pulls into the Asbury Park station and the gates are already down, assuming the train isn't stopping. And now, the interlocked traffic signal at Corlies and Memorial Drive has turned everything into an "all stop" situation, and motorists are getting antsy, and the gates go up. But if the train starts moving again, the gates come down again, after maybe three cars get to cross the rails.

Rt 33 / Corlies Ave. is a very busy road, especially during rush hours and horrible during the summer, traffic backed up sometimes to Route 35 due to those gates.


yep- as long as i can remember (like 40 years now)- they just inch up to the gates again after the time out after the initial drop. No button, phone call, bill/whistle receiver, or anything like this. Unless things have changed that's all there is to it.
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Re: Grade crossings next to stations -- how do they work?

Postby SemperFidelis » Fri Mar 03, 2017 11:37 pm

One of the best places to see this in action is Dover at rush hour. The grade crossing is about 20 feet off the end of the platform.

I have very faint memories of watching this same grade crossing on my life's earliest trainwatching trips with my father at Dover in the late 1970s and early 1980s. Those days of ancient (but still my favorite) Lackawanna MUs, U34 NJDOT Bluebirds (second favorite), early Bombardier coaches (I think), ancient track and signalling infrastructure that probably came on line the same day as the MUs, and a backlog of deferred maintenance that makes today's issues look so simple in comparison.

Back then, it was anyone's guess as to whether the gates would go down, stay down, come back up, or some combination of any of those outcomes. I recall, many times, seeing someone from the train crew access a box near the crossing gates to (I presume) flip some sort of switch so the gates would actually go down. I was incredibly young so I might be misremembering, but that is what my father explained to me at the time...or what I think he was saying.

People back then, as they probably still do, were so impatient and/or frustrated at the dysfunctional operation of the system that they would regularly drive around the gates. I don't know if Dover has quad gates or cameras now, but it was very, very common to see back then.

Does anyone else remember the small cowcatchers on the MUs and how they would be painted red, blue, or yellow? Was there any reason for this color coding, or was it just a matter of what bright paint they had laying around the shops at the time?

I remember being so upset upon news that the MUs were being pulled off that I cried in my bed. I apparently tought that my father was saying that the whole railroad was being abandoned and that there would be NO TRAINS at all at Dover anymore. When he explained that there would be new, shiny Arrows, I was able to fall asleep. That is one of my earliest memories... :-)
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Re: Grade crossings next to stations -- how do they work?

Postby 130MM » Fri Mar 17, 2017 8:12 am

GSC wrote:Put simply, the gates "time out". This is a very common occurrence at the Corlies Ave. Route 33 crossing in Neptune. The westbound train pulls into the Asbury Park station and the gates are already down, assuming the train isn't stopping. And now, the interlocked traffic signal at Corlies and Memorial Drive has turned everything into an "all stop" situation, and motorists are getting antsy, and the gates go up. But if the train starts moving again, the gates come down again, after maybe three cars get to cross the rails.

Rt 33 / Corlies Ave. is a very busy road, especially during rush hours and horrible during the summer, traffic backed up sometimes to Route 35 due to those gates.


The thing no one has mentioned is that these crossing are what is called "motion detector". When the train stops, the signal system detects that there is no motion, and starts a timer. If there has been no motion detected in the duration of the timer, the gates go up -- hence the term "timed out". Once the train starts moving again, the gates are lowered again. The engineer is then required to ensure the flashers have been operating for at least 20 seconds, or the gates are horizontal, before occupying the crossing.

The situation GSU described often happens. The public sees the gates going up and down, and thinks there is something wrong - especially if they are the fourth car when only three make it through.They call it in, and the dispatcher has to issue Form D's until the maintainer gets there, and gives the Clear On Arrival - Gates Operating as Intended. On some of our crossings, C&S has cut out the motion detector, and just left the gates down. It eliminates the complaints and confusion, but makes people wait longer.

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Re: Grade crossings next to stations -- how do they work?

Postby JPG76 » Sat Mar 18, 2017 12:49 pm

The crossing gates in Dover actually don't have a "time out". There are dispatcher controlled interlocking signals at the West end of the platform. The crossing gates are wired in a way that they do not activate for westbound trains if those signals are at stop.
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Re: Grade crossings next to stations -- how do they work?

Postby MattW » Sat Mar 18, 2017 2:20 pm

JPG76 wrote:The crossing gates in Dover actually don't have a "time out". There are dispatcher controlled interlocking signals at the West end of the platform. The crossing gates are wired in a way that they do not activate for westbound trains if those signals are at stop.

As someone with a bit of an engineering background, that seems kinda dangerous by not being fail-safe. A stop signal (even with ASES[?]/PTC/cab signaling) is no guarantee something won't go through it.
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Re: Grade crossings next to stations -- how do they work?

Postby Nasadowsk » Sun Mar 19, 2017 1:19 pm

MattW wrote:
JPG76 wrote:The crossing gates in Dover actually don't have a "time out". There are dispatcher controlled interlocking signals at the West end of the platform. The crossing gates are wired in a way that they do not activate for westbound trains if those signals are at stop.

As someone with a bit of an engineering background, that seems kinda dangerous by not being fail-safe. A stop signal (even with ASES[?]/PTC/cab signaling) is no guarantee something won't go through it.


The LI has this at New Hyde Park. If a train sits long enough at a station, the ASC drops to restricting and the gates pop up a few seconds later. I would imagine / hope that the system has some sort of way of telling the train is sitting there. I'm not sure though. I thought some grade crossing setups had a way to predict train speed?
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Re: Grade crossings next to stations -- how do they work?

Postby ExCon90 » Sun Mar 19, 2017 1:51 pm

There are some posts somewhere stating that speed measurement won't work in electrified territory because of the presence of the return circuit.
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Re: Grade crossings next to stations -- how do they work?

Postby JPG76 » Tue Mar 28, 2017 8:03 pm

MattW wrote:
JPG76 wrote:The crossing gates in Dover actually don't have a "time out". There are dispatcher controlled interlocking signals at the West end of the platform. The crossing gates are wired in a way that they do not activate for westbound trains if those signals are at stop.

As someone with a bit of an engineering background, that seems kinda dangerous by not being fail-safe. A stop signal (even with ASES[?]/PTC/cab signaling) is no guarantee something won't go through it.


It is also set up so that the gates would immediately activate if a train does roll past a stop signal.
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Re: Grade crossings next to stations -- how do they work?

Postby Kilgore Trout » Fri Apr 07, 2017 11:07 am

To take Radburn as an example, IIRC, the gates will always go down when a train is in the station, even if only going westbound.
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Re: Grade crossings next to stations -- how do they work?

Postby OportRailfan » Fri Apr 07, 2017 12:57 pm

MattW wrote:
JPG76 wrote:The crossing gates in Dover actually don't have a "time out". There are dispatcher controlled interlocking signals at the West end of the platform. The crossing gates are wired in a way that they do not activate for westbound trains if those signals are at stop.

As someone with a bit of an engineering background, that seems kinda dangerous by not being fail-safe. A stop signal (even with ASES[?]/PTC/cab signaling) is no guarantee something won't go through it.


ASES/PTC? That's no existent on NJT at the moment. Plus they ripped out all the Alstom ASES stuff they did have on the Pascack Valley Line.
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