ITCS Train control
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George Harris
Engineer
Makes the FRA happy.
Well, maybe that is a little cryptic for those that are unfamiliar with the way regulation works.
For a train to run 80 mph or faster there must be some form of additional system beyond the normal signal system, such as cab signals, ATS (automatic train stop) or ATC (automatic train control).
The 80 mph or faster clause is the reason for the proliferation of 79 mph speed limits.
Well, maybe that is a little cryptic for those that are unfamiliar with the way regulation works.
For a train to run 80 mph or faster there must be some form of additional system beyond the normal signal system, such as cab signals, ATS (automatic train stop) or ATC (automatic train control).
The 80 mph or faster clause is the reason for the proliferation of 79 mph speed limits.
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It's biggest and most primary function is that it can and will stop the train if the engineer misses a red signal. So had this been in place on the California Metrolink system late last year, that horrific crash might not have occured at all, or at least the trains would have both been moving much slower by the time of impact thanks to ITCS.
Is there regulation on how far apart signal lights are? Dose the dispatcher have to manually givea
train a green or is that automatic if nothing is in the way before the next signal? I live fairly close to
the Wolverine tracks in Mi , I notice that the signal is either red or yellow and it will turn green
and within a few minutes the train will pass and I wondered if the green was triggered by the train
passing the previous signal?I assume it is ,but I am still at the elementery level when I it comes to
understanding how the system works!!!!
Thanks !
Trainfan
battalion51
Engineer
Well in general there are two basic types of signaling systems that are used across the country, ABS and CTC. ABS is very basic, and generally works best in a single direction only. ABS keeps at least two blocks (signals) in between each train. If a train is occupying a block then the signal will be red. If there is one block clear the signal will be an approach (yellow). If there are two blocks the signal will be clear (green). ABS cannot control switches or anything like this. This system is generally used in double track areas where there will be one track for one direction, and the other for the opposite direction.
There's also CTC, CTC uses a computer system and a link to that computer to control the signals and switches. The principles of ABS are still in place as far as controlling distance between trains. However the dispatcher can line a switch a certain way and this will effect the signals that a train receives. So for example if a train is going to have to crossover there will be at least one signal preceding the crossover that will alert the train to slow down. Also, if a switch is not lined for the train there will be an approach signal (yellow) prior to the red signal. Once the dispatcher lines up the tracks for a train and that track is clear, generally the signals will go ahead and light up accordingly. In areas with limited movements the signals will be lit for many miles ahead of the train. That's the basics of signaling.
There's also CTC, CTC uses a computer system and a link to that computer to control the signals and switches. The principles of ABS are still in place as far as controlling distance between trains. However the dispatcher can line a switch a certain way and this will effect the signals that a train receives. So for example if a train is going to have to crossover there will be at least one signal preceding the crossover that will alert the train to slow down. Also, if a switch is not lined for the train there will be an approach signal (yellow) prior to the red signal. Once the dispatcher lines up the tracks for a train and that track is clear, generally the signals will go ahead and light up accordingly. In areas with limited movements the signals will be lit for many miles ahead of the train. That's the basics of signaling.
Joel N. Weber II
Engineer
It should be pointed out here that the Canadians do run trains at speeds at least a little faster than 80 MPH without any cab signals or automatic train stop.
Yes, 100 mph on several routes including Montreal - Toronto and Montreal - Ottawa.
Automatic Block Signals (ABS) are generally an overlay system that provides protection to prevent train collisions. ABS normally does not authorize movements except when there is a current of traffic with trains usually traveling in one direction on a given track. An ABS system will trigger more restrictive signal indications based on the occupancy in a block of a train or a switch open. ABS can also provide warning if there is any anomaly that would cause current to not travel through the track. This could be a broken rail, or something shunting the circuit.
If no trains are in a close proximity to ABS signals, the signals will remain as clear (green). CTC involves the adoption of bi-directional ABS signaling and control points (interlockings). A control point contains a signal that the dispatcher has control over and switches or other on track devices. The dispatcher manually selects the route, and lights up the signal. The dispatcher does not have control over the type of signal that will be displayed, only whether he or she wants the signal to be at stop or go. In a typical CTC signal system between the control point signals will be intermediate signals, which give advanced warning to the train. Intermediate signals function like ABS signals with the exception that they provide additional information about the next signal at the control point.
A positive train control system analyzes the trains speed, track profile, train type and signals to determine if the engineer is operating within the defined safety window. If the computer thinks the engineer will not be able to stop the train to comply with a signal it will require and enforce the reduction of train speed. Existing cab signaling systems can perform similar functions, depending on what type of system is in place.
Clear as mud?
This video from BNSF describes how their version of PTC works.
http://www.bnsf.com/media/etms_video.html
http://www.bnsf.com/media/etms_video.html
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George Harris
Engineer
That is because it is Canada. It is the US FRA. Last I noticed, Canada was still another country, so the FRA has no jurisdiction. They have their own set of regulations. The reason that equipment can freely run through is because of common industry standards, not laws. Same applies to Mexico.
MattW
Conductor
Just as a side note about ABS, there is a stretch of CSX between Scottdale, GA and Stone Mountain, GA east of Atlanta that is single-track ABS. There are no sidings until you get to Stone Mountain where I presume is changes to the DTC used east of there. It sort of makes sense, dispatchers control what trains leave controlled territory and keep the signals there for following trains.
Crescent ATN & TCL
OBS Chief
Most of the Crescent's route from MEI to NOL is single track ABS, NS and CSX seem to prefer ABS on moderate to low traffic lines and reserve CTC for High Traffic lines only.
George Harris
Engineer
Completely different subject. There are standards in the FRA that require the crossing circuit to give a certain minimum length of warning time. The time is the same, wheter the train speed is 10 mph or 100 mph.
Old style for crossing gates or flashers only, for that matter was a fixed length of circuit in the track based on maximum train speed. When a train entered the circuit, the cycle would start. Usually there was an "island" circuit close to the crossing itself that would allow the gates to go up and the flashers to quit as soon as the train cleared the crossing rather than continue until the train cleared the lenght of the circuit going out.
The problem with that form of approach is obvious. A slow train would cause the warning cycle to start way too soon.
Now there are predictor type circuits that can measure the train speed and start the cycle of crossing warning operation so as to achieve the required warning time whatever the train speed happens to be.
engine999 did a good job of explaining it, but if you'd like a somewhat thorough explanation that may also be geared a bit toward people unfamiliar with railroading operations (but may also be incomplete and/or inaccurate in some instances--it's a work in progress!), check out the following Wikipedia articles (disclaimer: yours truly was heavily involved in the writing of some of these 
):
http://en.wikipedia.org/wiki/North_America...ilway_signaling (the main article attempting to discuss all methods of operation and signaling in the U.S.)
http://en.wikipedia.org/wiki/Track_warrant and http://en.wikipedia.org/wiki/Direct_traffic_control (the two main base methods of granting authority underlying single-track ABS; dual-track ABS usually uses Rule 251 or similar rules where each track has a given direction or "current of traffic")
http://en.wikipedia.org/wiki/Automatic_Block_Signal (as engine999 mentioned, ABS is an overlay over an actual method of granting track authority; it allows higher volumes of train traffic with fewer cumbersome radio transmissions between trains and dispatchers)
http://en.wikipedia.org/wiki/Centralized_traffic_control (the evolution of ABS, where dispatchers control routes completely remotely and with virtually no radio communication needed)
http://en.wikipedia.org/wiki/Automatic_Train_Stop (one of the earlier methods of ensuring compliance with signals)
http://en.wikipedia.org/wiki/Automatic_Train_Control (a newer method of ensuring compliance with signals, including displaying cab signals--also see http://en.wikipedia.org/wiki/Cab_signalling--thereby reducing the reliance on trackside signals, and overspeed enforcement)
http://en.wikipedia.org/wiki/Positive_Train_Control (an overlay, of which ITCS is a part, on top of the existing methods of granting track occupancy authority which can provide virtually airtight compliance with track authority and governance)
Hopefully these help at least give you some basics or some ideas for further questions!
):http://en.wikipedia.org/wiki/North_America...ilway_signaling (the main article attempting to discuss all methods of operation and signaling in the U.S.)
http://en.wikipedia.org/wiki/Track_warrant and http://en.wikipedia.org/wiki/Direct_traffic_control (the two main base methods of granting authority underlying single-track ABS; dual-track ABS usually uses Rule 251 or similar rules where each track has a given direction or "current of traffic")
http://en.wikipedia.org/wiki/Automatic_Block_Signal (as engine999 mentioned, ABS is an overlay over an actual method of granting track authority; it allows higher volumes of train traffic with fewer cumbersome radio transmissions between trains and dispatchers)
http://en.wikipedia.org/wiki/Centralized_traffic_control (the evolution of ABS, where dispatchers control routes completely remotely and with virtually no radio communication needed)
http://en.wikipedia.org/wiki/Automatic_Train_Stop (one of the earlier methods of ensuring compliance with signals)
http://en.wikipedia.org/wiki/Automatic_Train_Control (a newer method of ensuring compliance with signals, including displaying cab signals--also see http://en.wikipedia.org/wiki/Cab_signalling--thereby reducing the reliance on trackside signals, and overspeed enforcement)
http://en.wikipedia.org/wiki/Positive_Train_Control (an overlay, of which ITCS is a part, on top of the existing methods of granting track occupancy authority which can provide virtually airtight compliance with track authority and governance)
Hopefully these help at least give you some basics or some ideas for further questions!
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