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  • New PTC signal heads, what will they mean?

    From Michael Moroney@21:1/5 to All on Sat Feb 19 01:46:54 2022
    At an entrance to an interlocking on a Massachusetts MBTA commuter rail
    line also used for freight (Fitchburg branch) they've added a signal
    head to each of two 3 high signals, at a lower level than the lowest
    existing head, but not in line with them. They also appear to have a
    white "S" painted on the back shade. So far I haven't seen this new
    head lit, the PTC system may not be active yet. Since noticing these
    heads are now facing trains (they were facing off to the side and
    covered in black plastic when first installed, so as not to confuse the engineer) I have only seen the other signals both displaying stop and
    hold (all red) or dark. Can anyone either explain its meaning, possible
    colors it may display or point me to a web page which does? Sorry my
    Google-fu isn't working for this one and I can't find anything.

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  • From Michael Moroney@21:1/5 to Michael Moroney on Sun Feb 20 17:13:55 2022
    On 2/19/2022 1:46 AM, Michael Moroney wrote:
    They also appear to have a white "S" painted on the back shade.

    Correction: "C", not "S".

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  • From Fishrrman@21:1/5 to Michael Moroney on Tue Feb 22 16:35:25 2022
    On 2/20/22 5:13 PM, Michael Moroney wrote:
    Correction: "C", not "S".

    I'm not familiar with the territory, but my guess is that
    the signal department is in the process of converting from
    fixed automatic block signals (between interlockings) to cab
    signals WITHOUT block signals.

    The "C" probably means "clear to next interlocking". It's
    used in other areas already.

    This would be displayed for a train that had suffered a cab
    signal failure, which would otherwise have to run at
    restricted speed (since the engineer has no way to ascertain
    the condition of the block ahead).

    In order for the "C" to be displayed, there has to be an
    "absolute block" (no other trains) from the affected train
    to the next interlocking ahead.

    The C means (the wording may vary from one railroad to another):
    "Trains and engines without operative cab signals may
    proceed on fixed signal indication, not exceeding 79mph, and
    approach next interlocking signal prepared to stop"

    At the next interlocking, the train must receive another "C"
    (along with fixed signal indication) in order to proceed
    further.

    It's really only for when the cab signals on a train have
    failed.

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  • From Michael Moroney@21:1/5 to Fishrrman on Wed Feb 23 11:59:04 2022
    On 2/22/2022 4:35 PM, Fishrrman wrote:
    On 2/20/22 5:13 PM, Michael Moroney wrote:
    Correction: "C", not "S".

    I'm not familiar with the territory, but my guess is that the signal department is in the process of converting from fixed automatic block
    signals (between interlockings) to cab signals WITHOUT block signals.

    The "C" probably means "clear to next interlocking". It's used in other
    areas already.

    This would be displayed for a train that had suffered a cab signal
    failure, which would otherwise have to run at restricted speed (since
    the engineer has no way to ascertain the condition of the block ahead).

    In order for the "C" to be displayed, there has to be an "absolute
    block" (no other trains) from the affected train to the next
    interlocking ahead.

    The C means (the wording may vary from one railroad to another):
    "Trains and engines without operative cab signals may proceed on fixed
    signal indication, not exceeding 79mph, and approach next interlocking
    signal prepared to stop"

    At the next interlocking, the train must receive another "C" (along with fixed signal indication) in order to proceed further.

    It's really only for when the cab signals on a train have failed.

    Thanks. Now that I had something better to search for, I found the same
    text, as well as a couple of videos (on other systems) which show the
    signal head active. It is a flashing lunar white.

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