Derailment Impacts 43(8) and 42(9)

Discussion in 'Amtrak Rail Discussion' started by Thirdrail7, Nov 9, 2019.

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  1. Nov 9, 2019 #1

    Thirdrail7

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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-stori...es-massive-derailment-in-hempfield/1006583026

     
  2. Nov 9, 2019 #2

    jis

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    Whatever happened to PTC? Precision Brake Failure?
     
  3. Nov 9, 2019 #3

    Thirdrail7

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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).
     
  4. Nov 10, 2019 #4

    jis

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  5. Nov 11, 2019 #5

    daybeers

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    How did they rear-end each other though?
     
  6. Nov 11, 2019 #6

    jis

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    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.
     
  7. Nov 12, 2019 #7

    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.
     
  8. Nov 13, 2019 #8

    Thirdrail7

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    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.
     
  9. Nov 13, 2019 #9

    daybeers

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    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?
     
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  10. Nov 13, 2019 #10

    jis

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    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.

    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.
     
    Last edited: Nov 13, 2019
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  11. Nov 18, 2019 #11

    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:

     
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  12. Nov 19, 2019 #12

    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.
     
    Last edited: Nov 20, 2019

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