Author Topic: Looking for an explanation of a signal aspect  (Read 296 times)

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peteski

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Looking for an explanation of a signal aspect
« on: Yesterday at 01:48:30 PM »
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Driving on Dascomb Rd. in Andover MA, parallel to the double track main, I noticed that the signals were lit up.  On the left side is was red, over red, over red.  The other one (I like to see explained) was yellow, over blinking green, over red.  What does that indicate?  The only knowledge of signals I have of from the old Kalmbach "How to operate your model railroad" book, and that just has very basic explanation (no blinking anything).
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DKS

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Re: Looking for an explanation of a signal aspect
« Reply #1 on: Yesterday at 01:53:01 PM »
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Do you know what the railroad is? Sometimes specific signal aspects are unique to specific railroads.
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C855B

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Re: Looking for an explanation of a signal aspect
« Reply #2 on: Yesterday at 02:08:08 PM »
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That's a toughie!

My edumaguess: Approach Limited  - prepare to reduce speed to X mph ['X' per RR's rulebook] by the next signal, in advance of a diverging route. Or something like that.

Do you know what the railroad is? Sometimes specific signal aspects are unique to specific railroads.

Likely the case here. Speed-indicating aspects are especially like this. In the two charts I checked, for a flashing green in either top two spots, UP is 30 mph, ATSF was 60 mph.
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DKS

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Re: Looking for an explanation of a signal aspect
« Reply #3 on: Yesterday at 02:08:18 PM »
+1
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peteski

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Re: Looking for an explanation of a signal aspect
« Reply #4 on: Yesterday at 02:21:08 PM »
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Do you know what the railroad is? Sometimes specific signal aspects are unique to specific railroads.

MBTA trains use those tracks, but it is probably Pan Am that owns them.
Here is the exact location in satellite view (I hope the link works): https://www.google.com/maps/@42.6440996,-71.1538728,70m/data=!3m1!1e3
It seems to me that Google maps (map view) used to indicate track better than they do now.  And it is Andover St. (I thought it was still Dascomb Rd).

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peteski

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Re: Looking for an explanation of a signal aspect
« Reply #5 on: Yesterday at 02:25:18 PM »
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Looking at this chart, it would be "limited" from the top row, but it has the red head grayed out?
These are fairly new LED signals (installed about a year ago).  In the past these signals were old searchlight type.
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C855B

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Re: Looking for an explanation of a signal aspect
« Reply #6 on: Yesterday at 02:38:48 PM »
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The matrix format of that chart is very unclear if not incorrect in some spots. Yellow/(red)/(red) is not "stop" in anybody's rulebook, it's "approach". Nonetheless, the grayed-out heads indicate the aspect applies for one- or two-head signals as well. Where the top head of three is shown grayed-out, you've got me.

"Advance warning" in the lower right? That's "advance approach" in my references.
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railnerd

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Re: Looking for an explanation of a signal aspect
« Reply #7 on: Yesterday at 03:07:32 PM »
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NORAC standards have more than you ever wanted to know about signals:

https://dms.ntsb.gov/public/58000-58499/58167/585157.pdf

-Dave

signalmaintainer

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Re: Looking for an explanation of a signal aspect
« Reply #8 on: Yesterday at 06:44:40 PM »
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It's "flashing," not "blinking." A sure foamer giveaway is to call it "blinking."

Looks like Approach Limited. Under my employer's rules, that's good for 60 mph in approach to a Diverging Clear over high-speed switch. But my employer uses speed-enhanced route signaling, not speed signaling.
« Last Edit: Yesterday at 06:49:02 PM by signalmaintainer »
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central.vermont

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Re: Looking for an explanation of a signal aspect
« Reply #9 on: Yesterday at 07:50:18 PM »
+1
Quoted from a conductor that runs this line.

"Approach limited. Means that  the next signal they come to will be a limited clear, and they’ll cross over to the other track."

Pete, those signals are what is called Vale interlocking.

Jon

peteski

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Re: Looking for an explanation of a signal aspect
« Reply #10 on: Yesterday at 09:23:13 PM »
+1
Thanks guys!
I think that back when they used the old B&M searchlight signals they did not use flashing aspects.

And yes, I'm more of a modeler than a prototype expert.  I actually specifically thought to make sure to use the term "flashing", but my true colors came through and I wrote "blinking".
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nkalanaga

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Re: Looking for an explanation of a signal aspect
« Reply #11 on: Today at 12:56:08 AM »
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I've seen aspects on the NS at Prichard, WV that aren't even in my ex-NP/BN "Consolidated Code of Operating Rules" rulebooks, so obviously there are regional differences as well as railroad differences.  Those books cover most Western railroads.
N Kalanaga
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signalmaintainer

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Re: Looking for an explanation of a signal aspect
« Reply #12 on: Today at 06:05:13 AM »
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I've seen aspects on the NS at Prichard, WV that aren't even in my ex-NP/BN "Consolidated Code of Operating Rules" rulebooks, so obviously there are regional differences as well as railroad differences.  Those books cover most Western railroads.

Also the difference between route signalling and speed signalling aspects very likely.
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cv_acr

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Re: Looking for an explanation of a signal aspect
« Reply #13 on: Today at 11:30:18 AM »
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The matrix format of that chart is very unclear if not incorrect in some spots. Yellow/(red)/(red) is not "stop" in anybody's rulebook, it's "approach". Nonetheless, the grayed-out heads indicate the aspect applies for one- or two-head signals as well. Where the top head of three is shown grayed-out, you've got me.

"Advance warning" in the lower right? That's "advance approach" in my references.

It's not giving it as stop...  the chart is a table/matrix showing what the indications are based on the speed restriction at the current signal (read the rows down) and the speed restriction at the next signal (read the columns across). The yellow is "clear" to "stop" (also known as "Approach" in older rule books; the modern Canadian Railway Operating Rules actually calls it "Clear to Stop" - they standardized the names as a "<speed> to <speed>" sort of convention and got rid of the word approach, which was a little overloaded - "Approach Medium", "Medium Approach [Stop]", etc.).

The flashing yellow aspect in the bottom corner is actually referred to as "Advance Clear to Stop" on Canadian railways.


The greyed out reds in the chart show that the indication can be given with or without those lights present on the signal. e.g. a single head signal displaying green is "Clear", but so is a three head signal showing G/R/R. "Slow to Clear" is R/G on a two head signal, or R/R/G on a three head signal.

The yellow over flashing green over red would definitely be a "Clear to Limited" [45mph] indication on Canadian roads. I'm guessing it's likely the same where you saw it, but as mentioned there are different rulebooks out there, so some signals may be slightly different on different railroads. I'm not sure the source of the specific chart either.

« Last Edit: Today at 11:33:48 AM by cv_acr »