On Thursday August 27th, PTC passed its first test. A cut of cars rolled away from a grain elevator at Bovina, TX on BNSF's Hereford Subdivision(part of the Transcon). The cars fouled Main 1 triggering the track circuit. A BNSF train that had passed the wayside signal governing that block received the stop indication via the PTC radio and the PTC system initiated immediate braking bringing the train to a stop 2400ft. short of the nearest car fouling the track.
The situation sounds comparable to the unplanned emergency braking that occurred during the first tests of the Westinghouse air brake.
Curiousity question - Would cab signals have provided the same (or similar) result?
I'm presuming the line does not have cab signals, and (PTC notwithstanding) relies on the lineside signals as the sole method of indicating track occupancy.
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tree68 Curiousity question - Would cab signals have provided the same (or similar) result? I'm presuming the line does not have cab signals, and (PTC notwithstanding) relies on the lineside signals as the sole method of indicating track occupancy.
Cars would have knocked cab signal down to restricting, requiring the crew to acknowledge and then react. The crew would have likely waited a few seconds to make sure it wasn't just a "flip" before applying brakes.
"Pure" PTC that relies on movement authorities and train location reporting from a lead locomotive - and not track circuits (other than for broken rail protection - perhaps) would NOT have stopped the train. Lose cars are not a train and have no way of reporting their position on the track.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
My understanding is that the ATSF used ATS (Autunatic Train Stop) that only activated when moving over a transponder at a signal location. ATC (Autunatic Train Control) used the tracks with coded 100 Hz current to provide for the cabsignal and speed limits. PTC Improves on these to provide much more information. The old ATS might not have stoped this train if there was no signal between the train and the incursion point of the car. Depending on where the signal was, ATS could have stopped the train if it had not passed a signal before the siding switch. Of course if the car fowled the track while the train was passing or just before people would say it didn't work/
Its good to see progress on PTC.
Automatic Train Control, cab signal systems that can enforce speed compliance with the cab signal aspect/indication would. Once the cab signal drops to a more restrictive indication, if you are moving faster than the new signal allows you only have a few seconds to either get under that speed or initiate a brake application. If you don't, the system will initiate a penalty brake application and open the PCS, reducing the engines to idle.
The comment about it happening in time for any system to react is correct. A few years ago at Ralston, IA we had a train strike West Central Co-Op's switch engine. Their little Plymouth engine, not their GP7. It had some kind of malfunction and started moving on it's own under power. It went over a flop-over derail without derailing and out on to our main track. It happened so close that even the emergency application couldn't stop them. At least there was enough time to cut their speed to about half of their maximum. It didn't derail the little engine, but gave it a good "bounce." The track is now equipped with a split-rail type derail.
Jeff
Electroliner 1935My understanding is that the ATSF used ATS (Autunatic Train Stop) that only activated when moving over a transponder at a signal location.
Correct.
Electroliner 1935ATC (Autunatic Train Control) used the tracks with coded 100 Hz current to provide for the cabsignal and speed limits.
ATC is another layer on top of cab signals which enforce the speeds associated with each signal aspect.
Electroliner 1935PTC Improves on these to provide much more information.
Sort of. It can have much more precise location of trains. As implemented, RRs are using track circuits and fixed block signals to drive movement authorities. So, in signalled territory, the I-ETMS version of PTC will know about shunted track circuits.
But, you don't HAVE to do it this way. Pure PTC does away with track circuits and relies soley on train position information (GPS, et. al.) to drive movement authorities. There won't be any track circuits to shunt, so loose cars or errant, unequipped trains will be invisible.
oltmanndBut, you don't HAVE to do it this way. Pure PTC does away with track circuits and relies soley on train position information (GPS, et. al.) to drive movement authorities. There won't be any track circuits to shunt, so loose cars or errant, unequipped trains will be invisible.
As was said loose cars are don't report a position. In the case at hand, if the train was already in the block, then the cars shunting the track might not have changed anything, the real trip of a restrictive PTC signal would have been a switch open or out of correspondence (run through) in the ahead of the train.
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dehusman As was said loose cars are don't report a position. In the case at hand, if the train was already in the block, then the cars shunting the track might not have changed anything, the real trip of a restrictive PTC signal would have been a switch open or out of correspondence (run through) in the ahead of the train.
Yes, it is my thought too that the siding switch must have reported its changed status, which caused the PTC system to trigger the brake application. BTW when BNSF resignalled the Hereford Subdivision they eliminated all the Intermediate Wayside signals, only the Absolutes remain. I am not sure if this means that there is only one signal block between absolute control points, but I think that is the only possible explaination.
dehusman oltmannd But, you don't HAVE to do it this way. Pure PTC does away with track circuits and relies soley on train position information (GPS, et. al.) to drive movement authorities. There won't be any track circuits to shunt, so loose cars or errant, unequipped trains will be invisible. As was said loose cars are don't report a position. In the case at hand, if the train was already in the block, then the cars shunting the track might not have changed anything, the real trip of a restrictive PTC signal would have been a switch open or out of correspondence (run through) in the ahead of the train.
oltmannd But, you don't HAVE to do it this way. Pure PTC does away with track circuits and relies soley on train position information (GPS, et. al.) to drive movement authorities. There won't be any track circuits to shunt, so loose cars or errant, unequipped trains will be invisible.
But the car fouled the main and passed the insulated joints which did shunt the track circuit. No switch activity. The Michigan Amtrak PTC incident occurred when the signal maintainer left a test wire in place that defeated the switch shunt and allowed an Amtrak 110 mph Wolverine to enter the siding. Fortunately, it was able to stop without any significant damage.
So what speeds are allowed in unsignalled territory? Does PTC have any track circuit requirements.? Since loose cars are not monitored, does this happen frequently?
Electroliner 1935 dehusman oltmannd As was said loose cars are don't report a position. In the case at hand, if the train was already in the block, then the cars shunting the track might not have changed anything, the real trip of a restrictive PTC signal would have been a switch open or out of correspondence (run through) in the ahead of the train. But the car fouled the main and passed the insulated joints which did shunt the track circuit. No switch activity. The Michigan Amtrak PTC incident occurred when the signal maintainer left a test wire in place that defeated the switch shunt and allowed an Amtrak 110 mph Wolverine to enter the siding. Fortunately, it was able to stop without any significant damage. So what speeds are allowed in unsignalled territory? Does PTC have any track circuit requirements.? Since loose cars are not monitored, does this happen frequently?
dehusman oltmannd As was said loose cars are don't report a position. In the case at hand, if the train was already in the block, then the cars shunting the track might not have changed anything, the real trip of a restrictive PTC signal would have been a switch open or out of correspondence (run through) in the ahead of the train.
oltmannd
Passenger train speed in DARK territory is 59 MPH. Have no idea what it will be in DARK PTC territory.
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oltmannd [snipped - PDN] Cars would have knocked cab signal down to restricting, requiring the crew to acknowledge and then react. The crew would have likely waited a few seconds to make sure it wasn't just a "flip" before applying brakes. "Pure" PTC that relies on movement authorities and train location reporting from a lead locomotive - and not track circuits (other than for broken rail protection - perhaps) would NOT have stopped the train. Lose cars are not a train and have no way of reporting their position on the track.
So now envision a cut of runaway cars heading downgrade at a pretty good speed (something just like that happened to an MBTA train in Boston about 5 years back, when a car delivered by a CSX crew later got away from a lumber yard). The approaching train reduces its speed to be able to stop in half the visible distance, as required by the rules- but then these cars come roaring around a curve, at way more than the appropriate speed, and they're not going to be slowing or stopping, either.
What result ? Is a collision likely, even if the train gets to a stop ? What if the approaching cars get to the train before it has either the time or distance to stop ? Will PTC do anything to prevent this scenario ? (I doubt it.)
- Paul North.
This youtube video of a Surfliner cab ride on the LA-San Diego BNSF route shows a speed and signal display in a cab. It was posted in 2009. Is this a precurser to PTC or a part of it? Or is it part of a computer simulation?
https://www.youtube.com/watch?v=N4UgarjFC_A
This one is posted on 5-2015.
https://www.youtube.com/watch?v=enjR_xRsgjA
It has a signal display that includes multiple indications and verbal notifications plus an allowed speed display with the actual speed.
Does BNSF have PTC in operation on this line?
Paul, runaway cars do shunt the track circuit. Only equipment deliberately equipped with insulated wheels, like some track speeders, M/O/W equipment, have such wheels, and they may be outlawed now. But you are correct, that shunting the track circuit may not be enough. The train facing the runaway faces a restrictive, then a red signal, but if the runaway is fast enough, the protection may not be enough. In this case the PTC does pervent ignoring the signals, but may not prevent contact. It does nothing, obviously, to stop the runaway, and the runaway can contact the standing train or the train before it stops.
But another possibility is that the location of the runaway will make its presence known on the dispatchers computer line simulation, and if he is alert, he will control the situation, aligning a diverting switch or alerting someone at lineside to act to derail the runaway at a non-hazardice location. Anyway, it still takes human beings to run a safe railroad.
As far as I know, the continued use of track circuits is one reason railroads are not going to pure PTC. Posssibly a new development is needed that combines the added safety of track circuits and the flexibility of pure PTC. Global positioning would be supplemented by high-frequency ac signals applied from the locomotive to the track, with the impedence constantly compared with what is expecte from the known configuration of the track layout, and when an unanticipated reflection occurs, a danger is understood.
daveklepper But another possibility is that the location of the runaway will make its presence known on the dispatchers computer line simulation, and if he is alert, he will control the situation, aligning a diverting switch or alerting someone at lineside to act to derail the runaway at a non-hazardice location. Anyway, it still takes human beings to run a safe railroad.
Let's not try to throw more responsibility on Train Dispatchers than they already have. Track circuits come on for a variety of legitmate reasons that have nothing to do with run-a-way equipment; a Dispatchers first thought about a track circuit coming on by itself has nothing to do with equipment on the track and everything to do with a possible track defect.
Secondly, at least on my carrier, as the signal system upgrades are taking place to support PTC the number of track segments on the model boards are being reduced to a single segment between control points. With a single segment, it is impossible to determine if a 'unidentified' cut of cars is moving - and even in locations that have multiple track segments identified on the model board, those segments may encompass 8 to 10 or more miles.
People tend to think signal systems are more sophisticated than they are. The signal system only knows it has an occupancy, the track shunted. It doesn't know why. A run away cut looks the same as a non-controlled switch open as a cut on the main as a broken rail as a train sitting there.
For example in the runaway cars example, the question is what does "in the block" mean? If it means that the train had passed the last intermediate signal before the switch, then I doubt the cut of cars by themselves, shunting the track or not, would have given the train a restictive signal. If the train was past the intermediate then the block was shunted, the track was occupied. Putting cars in front of it would be indistinguishable from the train itself to the signal system. Most signal systems don't have the sophistication to tell if there is an unoccupied peice of track between to occupancies. The signal system expects the track to be occupied in front of the present location of the train, that happens all the time.
The only thing that would be detectable, if the train had passed the intermediate signal prior to the switch, is the switch being run through (out of correspondence) in front of the train.
As far as track circuits go, I don't see railroads getting rid of them any time soon. They add too much safety. I can tell from the comments that many of the people on this list are solely focused on movement authority. Railroads have to take the whole picture into account. Getting rid of the track circuits reduces safety and cannot be replaced by all the GPS in the world. Having the engine detect occupancy will work right up until the first time a train applies sand and the engine is instantly insulated from the rails.
daveklepper ........... But another possibility is that the location of the runaway will make its presence known on the dispatchers computer line simulation, and if he is alert, he will control the situation, aligning a diverting switch or alerting someone at lineside to act to derail the runaway at a non-hazardous location. ..........................
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But another possibility is that the location of the runaway will make its presence known on the dispatchers computer line simulation, and if he is alert, he will control the situation, aligning a diverting switch or alerting someone at lineside to act to derail the runaway at a non-hazardous location.
Aligning a switch to divert the runaway may be desired but not possible. If the route for the train has already been cleared through a control point there will be a delay of up to several minutes for the interlocking logic to time out once the signal has been cancelled. Also, rarely do switches controlled by the dispatcher lead to a dead-end track where the runaway can be safely derailed. Instead they will take another mainline track, or pop back out at the end of a passing siding (unless they are going too fast for a low speed turnout). The same "time-out" delay may also prevent the dispatcher from diverting the train out of the path of the runaway.
The chances of finding anybody at lineside with modern staffing levels is minimal. Even if there is, for them to arrange something that might derail the oncoming cars will take time that may not be available.
John
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