Derailment Impacts 43(8) and 42(9)

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Thirdrail7

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There is a derailment west of Altoona. There doesn't appear to be a word about the crew. I hope they're ok. At any rate, 43 terminated and will turn for 42(9) at HAR.

Keep an eye on the website for updates but I doubt it will change. Click on the link for pictures.

https://www.wpxi.com/news/top-stories/collision-between-trains-causes-massive-derailment-in-hempfield/1006583026

Collision between trains causes massive derailment in Hempfield

HEMPFIELD TOWNSHIP, Pa. - A collision caused dozens of train cars to go off the tracks in Hempfield.

A Norfolk Southern mixed-freight train heading west from Altoona to Conway collided with the back of a Norfolk Southern intermodal train – which caused the massive derailment, officials confirmed.
 

jis

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Whatever happened to PTC? [emoji848] Precision Brake Failure? [emoji57]
 

Thirdrail7

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Whatever happened to PTC?
Positive Train Collision.

PTC can't stop everything. There are still plenty of opportunities for incidents on the rails.

At any rate, the cleanup is lagging, so 43(9) terminates at HAR and turns to 42(10).
 

daybeers

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Positive Train Collision.

PTC can't stop everything. There are still plenty of opportunities for incidents on the rails.

At any rate, the cleanup is lagging, so 43(9) terminates at HAR and turns to 42(10).
How did they rear-end each other though?
 

jis

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How did they rear-end each other though?
That indeed was my question too. Everything else seems to have followed the original causative collision. That is why I surmised brake failure of some sort, since no amount of PTC can prevent the failure of brakes.
 

Barb Stout

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One of the commenters on the article that jls posted indicated that PTC is not in use on this line.
 

Thirdrail7

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One of the commenters on the article that jls posted indicated that PTC is not in use on this line.
Even if PTC is installed, some of it will stop rear-end collisions. Some forms of PTC won't even stop head-on collisions. It will keep them at low speeds. Additionally, all the PTC in the world won't stop something from hitting a train that is derailing right in front of your movement.
 

daybeers

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I'm sorry for being naïve, but even without PTC, how can there be a rear-end collision with the signal system? If the two trains were on the same track, the block should be red for the train following, correct?

What head-on collisions can PTC not prevent?
 

jis

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I'm sorry for being naïve, but even without PTC, how can there be a rear-end collision with the signal system? If the two trains were on the same track, the block should be red for the train following, correct?
SPAD. Signal Passed At Danger. The Engineer of the rear train ignoring the Red Stop signal. Or even in the presence of PTC the rear train could be a runaway with non-operative brakes which no amount of PTC can stop.

What head-on collisions can PTC not prevent?
Failure of the braking system in one of the trains thus failing to stop before fouling the track of an oncoming train that is too close to manage to stop when the signal drops in front of it. There will be odd race condition that you can't do anything about.
 
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Thirdrail7

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Adding on the Jis' statement, there are plenty of times when trains are authorized to be in the same block. A great deal of the current versions of PTC can not help out in these circumstances.

A brief fair use quote from Three NS Trains Collide in Western Pennsylvania should help you understand:

PTC enforces a railroad’s maximum restricted speed (15/20 mph), but is unable to determine the exact position of obstructions ahead (a stopped train, broken rail, improperly lined switch, etc.). PTC also cannot determine “half the range of vision” for a railroad’s restricted-speed rule. Based on Federal Railroad Administration RSAC (Railroad Safety Advisory Committee) proceedings, the acknowledgement was that PTC would mitigate the severity of restricted-speed accidents.

The current version of PTC, which is mandated to be fully implemented in the U.S. by Dec. 31, 2020, does not, through an EOT (end-of-train device), determine the position of the rear of a train and transmit that telemetry to a following train via the wayside and central office PTC equipment. As well, it will not prevent certain low-speed collisions caused by permissive block operation (more than one train in a block), accidents caused by trains “shoving” in reverse, derailments caused by track or train defects, grade crossing collisions, or collisions with previously derailed trains. Where PTC is installed in the absence of track circuit blocks (“dark territory”), it will not detect broken rails, flooded tracks, or debris fouling the right-of-way.[/url]
 

jis

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Thirdrail, thanks for the quote. I have had a heck of a time trying to explain these issues to people who think they are making very learned statements about what PTC can or cannot do and its limitations.

This is the reason that ETCS, the much denigrated in the US by some, European architecture for train protection and control systems, has three different levels, each higher level providing specific higher level of protection. The US PTC is a one size fits all attempt geared towards running long freight trains with uneven operating characteristics through corn fields with relatively low traffic, and then trying to get it to do stuff it is not designed for. The outcomes are as obvious as the night follows the day.

But truth be told, not knowing the location of the end of a train is the one that blew my mind when I learned about it. PTC without track circuits or axle counters (whatever that amounts to) is basically incapable of determining whether the tail of a train has cleared a fouling mark or not.
 
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