In real life we don't need or use ATLS triggers, slaves, or controllers to tell the crossing arms when to go down and have the lights flash and the bell ring. I don't exactly know how it's configured in real life but depending on the speed and the distance of the train, the crossing will go down when a train has gotten to a certain distance of the XING. This would be extremely useful when there's a crossing with a train parked in a siding waiting for track clearance and is starting up or is slowing down into a siding or on the mainline. But the train could also be speeding up. What is your guys' thoughts?
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Railroad Crossing Sensors
- Thread starter Kris94
- Start date
In real life the system works almost identically to ATLS. At a set distance from the crossing the train completes an electrical circuit through the track which brings the gates down, sets bells ringing etc. After passing the crossing it completes another circuit that brings the gates up.
You can make ATLS allow for some trains getting closer or rolling stock being parked by either setting the ATLS triggers to ignore one priority setting, or setting ATLS triggers on sidings closer to the crossing or using ATLS driver commands to trigger the crossing.
All in all as close to 'realistic' as any Trainz crossing system is likely to get....
You can make ATLS allow for some trains getting closer or rolling stock being parked by either setting the ATLS triggers to ignore one priority setting, or setting ATLS triggers on sidings closer to the crossing or using ATLS driver commands to trigger the crossing.
All in all as close to 'realistic' as any Trainz crossing system is likely to get....
stagecoach
75377
You might find this in depth doc will give you a lot of information on level crossings in the Uk.
http://www.rail-reg.gov.uk/upload/pdf/level_crossings_guidance.pdf
http://www.rail-reg.gov.uk/upload/pdf/level_crossings_guidance.pdf
More modern grade crossing signals in the US do not use a set distance; rather, the microprocessor in the controls determines the speed of the train, and causes the crossing signal to activate a fixed time (I think on the order of 20 to 30 seconds, and the time may vary depending upon details of the configuration of the crossing) before the train is calculated to enter the crossing. A train moving at 10 mph will activate the crossing a couple of hundred feet from the crossing, a train moving at 60 mph will activate the same signal from a half a mile away.
This is not to say that all crossings have the most modern equipment. Railroads operate very much on the "if it ain't broke, don't fix it" strategy, and I expect there are a number of location swhere the signals operate on the fixed distance method, and I know there are some which don't have automatic signals at all.
ns
This is not to say that all crossings have the most modern equipment. Railroads operate very much on the "if it ain't broke, don't fix it" strategy, and I expect there are a number of location swhere the signals operate on the fixed distance method, and I know there are some which don't have automatic signals at all.
ns
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In fact, ATLS could be speed dependent. There's no reason why the ATLS Trigger could not check the speed of the train and delay the crossing activation accordingly, (for slow trains).
I didn't write it like that because I was worried that ATLS wouldn't know if the speed changed after the train had left the Trigger.... so it could be fooled!
It could be done though..... Maybe a future update!
Boat
I didn't write it like that because I was worried that ATLS wouldn't know if the speed changed after the train had left the Trigger.... so it could be fooled!
It could be done though..... Maybe a future update!
Boat
I suppose I could go searching for it, but the tracks that parallel my route to and from my place of employ have many level crossings through the three tracks. I have seen both freights and passenger consists waiting at various distances from a crossing. They may be right on top of the intersection, ten yards to infinity away, but the crossing is not activated. I have seen the crossings activate without a train in sight as well. I have seen a scoot held at a red while another gets the green around it, activating the signals.
So, my point is; obviously the contact completing the electrical circuit, yes. Not just that though, there must be something else as well.
So, my point is; obviously the contact completing the electrical circuit, yes. Not just that though, there must be something else as well.
Hi Kris. (and this is for you too Boat) ...A couple of years ago I worked on the development of Level crossing predictors to be used in Scandinavia. They were having too many accidents at unmanned level crossings. A visual for you is the standard LOC that you will find alongside the track in either stainless steel or grey. I will not go into the electrical what-have-you but a series of relays linked through track sensors and signals will set the gates and signals as required.A resistance measurement is constantly checked in micro seconds from a given point (starting) on the track. Depending on the speed limit for that track then the starting distance is placed from a point where the train should be able to stop BEFORE the crossing. The gates and bells / lights will be activated at the starting distance on the track measurement. A repeater will sound in the cab that this has been activated. A constant tone will indicate to the driver that the signals/gates have failed giving the driver time to slow his engine.
That is about the basics of it.
Boat... as an update you might need to consider the set track speeds (speedboards) can all be different. You might need to include a speed trigger at "X" distance from the crossing so ALL trains will cross at the same speed and your ATLS will be able to cope with it.
Taken from the Network rail guide to crossings - "The speed of the trains over the crossings will be determined by the traffic moment but should not exceed 56 mph at any time. A maximum time allowance is relative but not more than 75 seconds"
Regards Doug
That is about the basics of it.
Boat... as an update you might need to consider the set track speeds (speedboards) can all be different. You might need to include a speed trigger at "X" distance from the crossing so ALL trains will cross at the same speed and your ATLS will be able to cope with it.
Taken from the Network rail guide to crossings - "The speed of the trains over the crossings will be determined by the traffic moment but should not exceed 56 mph at any time. A maximum time allowance is relative but not more than 75 seconds"
Regards Doug
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This is my observation of grade Crossings in the U.S...
The track circuit detects the resistance of the rails. When no train is near, there is a high resistance. However, as a train approaches, the wheels/axles short across the rails, lowering the resistance seen by the track circuit. The track circuit reacts to the change in resistance. At a certain threshold the gates trigger. This allows for a fast train to trigger the gates at a farther distance then a slow train. If a train is going really slow (i.e. a couple miles an hour, a train can be very close before the gate trigger.
I've seen trains very slowly approach a crossing, then stop a short distance before it, without triggering the gates. Other times a train stopping short of a crossing may trigger the gates before it comes to a complete stop. Then the gates "time out" and go back up because the resistance wasn't changing. When the train starts up again, the resistance starts going down again, triggering the crossing. Then when the train passes the crossing, at any speed, the resistance goes up, causing the gates to go back up.
I remember being stop at a crossing with a very slow southbound train going across the crossing as it approach the south end of the siding. The road was wasn't very wide. When some long cars would go across the road and the axles were on either side of the road, the gates would start back up, then go back down when the next axle went across. The train finally stop at the south signal with no axles on the road. The gates went up and stayed up, even though there was a long car across the road. Then the northbound train approached on the mainline, triggering the gates again. By the time the end of the northbound crossed the road, the southbound was moving again holding the gates down until the end of the train. What an odd sight to see.
The track circuit detects the resistance of the rails. When no train is near, there is a high resistance. However, as a train approaches, the wheels/axles short across the rails, lowering the resistance seen by the track circuit. The track circuit reacts to the change in resistance. At a certain threshold the gates trigger. This allows for a fast train to trigger the gates at a farther distance then a slow train. If a train is going really slow (i.e. a couple miles an hour, a train can be very close before the gate trigger.
I've seen trains very slowly approach a crossing, then stop a short distance before it, without triggering the gates. Other times a train stopping short of a crossing may trigger the gates before it comes to a complete stop. Then the gates "time out" and go back up because the resistance wasn't changing. When the train starts up again, the resistance starts going down again, triggering the crossing. Then when the train passes the crossing, at any speed, the resistance goes up, causing the gates to go back up.
I remember being stop at a crossing with a very slow southbound train going across the crossing as it approach the south end of the siding. The road was wasn't very wide. When some long cars would go across the road and the axles were on either side of the road, the gates would start back up, then go back down when the next axle went across. The train finally stop at the south signal with no axles on the road. The gates went up and stayed up, even though there was a long car across the road. Then the northbound train approached on the mainline, triggering the gates again. By the time the end of the northbound crossed the road, the southbound was moving again holding the gates down until the end of the train. What an odd sight to see.
This is my observation of grade Crossings in the U.S...
The track circuit detects the resistance of the rails. When no train is near, there is a high resistance. However, as a train approaches, the wheels/axles short across the rails, lowering the resistance seen by the track circuit. The track circuit reacts to the change in resistance. At a certain threshold the gates trigger. This allows for a fast train to trigger the gates at a farther distance then a slow train. If a train is going really slow (i.e. a couple miles an hour, a train can be very close before the gate trigger.
I've seen trains very slowly approach a crossing, then stop a short distance before it, without triggering the gates. Other times a train stopping short of a crossing may trigger the gates before it comes to a complete stop. Then the gates "time out" and go back up because the resistance wasn't changing. When the train starts up again, the resistance starts going down again, triggering the crossing. Then when the train passes the crossing, at any speed, the resistance goes up, causing the gates to go back up.
I remember being stop at a crossing with a very slow southbound train going across the crossing as it approach the south end of the siding. The road was wasn't very wide. When some long cars would go across the road and the axles were on either side of the road, the gates would start back up, then go back down when the next axle went across. The train finally stop at the south signal with no axles on the road. The gates went up and stayed up, even though there was a long car across the road. Then the northbound train approached on the mainline, triggering the gates again. By the time the end of the northbound crossed the road, the southbound was moving again holding the gates down until the end of the train. What an odd sight to see.
Yes. This is exactly what I was looking for. I think if we had circuits in the tracks whenever we placed grade crossings, then that would be of great help.
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