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A Question For The Signal Experts Herein

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A Question For The Signal Experts Herein
Posted by blhanel on Sunday, September 19, 2021 7:58 PM

My wife and I are currently on vacation, and today we traveled from Marshfield, WI to Duluth, MN.  The first 20 or so miles of the journey followed the CN Superior Sub, which appears to be a well-maintained mostly single-track mainline.  Southeast of Marshfield there is a long passing siding, and six miles or thereabouts northwest is another passing siding near Spencer.  All of the signals along this stretch between them contain two heads.  As we left Marshfield and approached Spencer, the signal aspects were very interesting- just NW of Marshfield a signal showed flashing yellow over green; two miles further the next signal showed solid yellow over green; the last at the start of the Spencer passing siding was red over yellow.  My suspicion is that a north/west bound was lined into the siding at Spencer, where it would meet a south/east bound train.  Am I correct, and what do the signal aspects like this for CN mean?

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Posted by rdamon on Sunday, September 19, 2021 9:07 PM

Here is a chart that I have bookmarked..

https://signals.jovet.net/rules/CROR%20Signal%20Rules.pdf

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Posted by blhanel on Sunday, September 19, 2021 9:38 PM

So what I was seeing corresponded to 413, 407, and 430 (provided the last signal had the "DV" plaque on it, which I wasn't observant enough to notice, I was piloting my pickup down the highway).  Jives with my suspicions.  Was curious, though, because they don't look like the aspects that I'm used to seeing on UP/BNSF.

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Posted by jeffhergert on Sunday, September 19, 2021 10:52 PM

The CN in the US doesn't use the CROR book.  They use a United States Operating Rules book.  

This is a bit older chart from the CN-CORA Book that shows CN signals in the US.

Canadian National Rwy Signal Rules 2011/CORA version (railroadsignals.us)  

It may not be complete and certainly is not up to date.

Jeff

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Posted by SD70Dude on Monday, September 20, 2021 1:24 AM

The chart Jeff linked seems very similar to the current CROR and old UCOR signals, and uses the old UCOR names (the current CROR names are different, but the meanings are basically the same).

I had a look at our current USOR signal indications, there are some key differences from the CROR.  I'll break down each signal Brian encountered but he is correct, the northbound train was lined into the siding at Spencer, which is 12,530' with a speed limit of 40 mph (siding and turnout speeds are listed in the timetable). 

Flashing yellow over solid green is USOR 807, "Advance Approach Diverging".  Proceed prepared to enter diverging route at second signal at prescribed speed.

Solid yellow over solid green is USOR 808, "Approach Diverging".  Proceed, prepared to enter diverging route at next signal at prescribed speed.  Proceed prepared to stop at second signal.

Solid red over solid yellow is USOR 812, "Diverging Approach".  Proceed on diverging route at prescribed speed prepared to stop at next signal.

Greetings from Alberta

-an Articulate Malcontent

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Posted by blhanel on Monday, September 20, 2021 10:00 AM

Thanks, guys!

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Posted by Lithonia Operator on Monday, September 20, 2021 3:25 PM

Is a home signal only and always a home signal? And is a distant signal only and always a distant signal?

Or is it relative, and it's a moving target, depending on where the train is?

Like say I get to a distant signal, it's yellow on top, and below it is a red. Meaning go slow, be prepared to stop at signal X.

So I proceed at reduced speed. But when I get to the end of the block, I get another yellow over red.

So is former "home" signal X now the "distant" signal for the next signal, Y, which becomes the new home "home?"

Do you understand my confusion?

Or am I confusing ABS with CTC? Does ABS not have distant and home, and those are strictly CTC signals.

Still in training.


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Posted by tree68 on Monday, September 20, 2021 3:42 PM

I'm certainly not a signal expert, but...

There are intermediate signals, and interlocking signals.

I'll leave it to someone else to do a proper distinction.

That said, basic signals aren't hard to interpret.  Beyond red, yellow, green, stacked signals (usually two or three heads) can usually be interpreted as top signal is track speed.  Middle signal is medium speed, bottom signal is slow speed. 

Specific indications notwithstanding, even with speed signalling, a green/clear on the bottom head is usually an indication of a diverging route.  The middle head sometimes indicates a diverging route capable of higher speeds, such as mainline crossovers.

I've gotten used to the B&O CPLs at Deshler and can usually figure out what's happening.

 

 

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Posted by adkrr64 on Monday, September 20, 2021 3:53 PM

Lithonia Operator
Is a home signal only and always a home signal? And is a distant signal only and always a distant signal?

They are either one or the other. From NORAC (GCOR is probably similar):

HOME SIGNAL: A fixed signal governing entrance to an interlocking or controlled point.

DISTANT SIGNAL: A fixed signal used to govern the approach of a train to a home signal.

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Posted by mvlandsw on Monday, September 20, 2021 8:23 PM

Absolute signals can serve as a distant signal for the next absolute signal. On the CSX ex P&LE line between Pittsburgh and Versailles, Pa. there is a 17 mile stretch where all but one of the signals are absolute. Each signal serves in succession as the distant signal for the next absolute.

Mark Vinski

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Posted by BaltACD on Monday, September 20, 2021 9:15 PM

mvlandsw
Absolute signals can serve as a distant signal for the next absolute signal. On the CSX ex P&LE line between Pittsburgh and Versailles, Pa. there is a 17 mile stretch where all but one of the signals are absolute. Each signal serves in succession as the distant signal for the next absolute.

Mark Vinski

In Automatic Block Signal territory - effectively every signal is a 'Distant Signal' for the signal that follows it.

The term 'Distant Signal' was mostly developed for DARK TT&TO territory where there were intersecting lines that crossed each other at grade.  The Distant Signal  normally displayed a 'Restricting' indication - 'Proceed at restricted speed approaching next signal prepared to STOP'.  The next signal would be the Absolute Signal protecting the diamond of the crossing railroad.

Riding the B&O's Lower CL&W Sub between Warwick and Holloway, Ohio, TT&TO territory the line crossed several other railroads at grade.  CR at Mace, 2 N&W lines at Justus, CR at Dover and also at Uhrich.  Each location had a Distant Signal in each direction to pre-warn the crews of the upcoming Absolute signal.

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Posted by jeffhergert on Tuesday, September 21, 2021 1:14 PM

adkrr64

 

 
Lithonia Operator
Is a home signal only and always a home signal? And is a distant signal only and always a distant signal?

 

They are either one or the other. From NORAC (GCOR is probably similar):

HOME SIGNAL: A fixed signal governing entrance to an interlocking or controlled point.

DISTANT SIGNAL: A fixed signal used to govern the approach of a train to a home signal.

 

GCOR no longer uses the term "Home" signal.  We have an Absolute Signal and an Interlocking Signal instead. 

A Distant Signal is marked with a D plate and used in unsignalled territory.  The rule book allows three aspects and indications; Distant Signal Clear, Distant Signal Approach, and Distant Signal Approach Diverging.  In practice, the ones I've seen continually display the Distant Signal Approach.

It should be remembered, Distant Signals (as used in GCOR) aren't block signals.  They don't show the condition of the track between the signal and the next one at an interlocking or control point.  That is why they (ours) don't show a stop indication.

Jeff  

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Posted by cv_acr on Tuesday, September 21, 2021 2:57 PM

Lithonia Operator
Is a home signal only and always a home signal? And is a distant signal only and always a distant signal?

Or is it relative, and it's a moving target, depending on where the train is?

Like say I get to a distant signal, it's yellow on top, and below it is a red. Meaning go slow, be prepared to stop at signal X.

So I proceed at reduced speed. But when I get to the end of the block, I get another yellow over red.

So is former "home" signal X now the "distant" signal for the next signal, Y, which becomes the new home "home?"

No. Nothing changes relative to where the train is. The signals are fixed.

A "home" signal is a controlled signal for an interlocking/control point. It's controlled by the tower operator or dispatcher.

A "distant" signal is one in advance of the interlocking/control point. It's dependent on the home signal, and is not directly controlled itself.

And technically if we're being semantic there is a difference between a "distant" signal and a block signal, as described above. CTC/ABS technically wouldn't have "distant" signals per the strict definition above, but there will be home/absolute/interlocking signals at each CTC control point and passive block signals in between.

The interlocking signals are controlled by the dispatcher, and default to their most restrictive indication, Stop. The "all-red" aspect on an interlocking signal is "Stop".

Block signals are purely passive, no direct control, and their indication is automatically based on the track occupancy, turnout positions, and what the next signal down the line is showing. The default indication for a block signal could be "Clear". The "all-red" aspect on a block signal is "Stop and Proceed".

ABS consists of only the second type of signals; purely automatic and only giving passive information on the track conditions.

A simplified way of thinking of CTC is a series of remotely-controlled interlockings with ABS block signals in between. (It's a little more sophisticated, but start there.)

Block signals are ALWAYS based on the block occupancy and the indication of the next signal down the line. But "next signal down the line" is NOT the definition of "home" signal. There could be several blocks in between interlockings/control points with "home" signals, meaning you encounter several block (not "home") signals in a row. No interlocking/control point = no "home" signal. Also note that "home" signals indications are ALSO influenced by whatever the next signal down the line is (usually a block signal, but could be another interlocking nearby)... unless the signal system simply ends past that point (dark territory) and there is no next signal.

In your example, neither X nor Y was a home signal... or either or BOTH of them could have been home signals... it's about the track layout and physical location of the signals, not the progression of your train.

http://www.lundsten.dk/us_signaling/signalbasics/

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Posted by Lithonia Operator on Tuesday, September 21, 2021 7:17 PM

Thanks all.

Chris, your explanation is particularly helpful. Yes

Still in training.


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Posted by zugmann on Tuesday, September 21, 2021 9:26 PM

--

   The opinions expressed here represent my own and not those of my employer or any other railroad, company, or person.

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Posted by Lithonia Operator on Tuesday, September 21, 2021 10:03 PM

Zug, that's hard to argue with.

Still in training.


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Posted by Lithonia Operator on Thursday, September 23, 2021 5:26 PM

I see heads that have three lamps in them: green, yellow, red.

Is any more than one of the lamps ever lit at a time? I am thinking No, and that if you want green over yellow over red, you would need three heads. Correct?

Still in training.


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Posted by tree68 on Thursday, September 23, 2021 7:00 PM

Lithonia Operator
I see heads that have three lamps in them: green, yellow, red.

I think that's pretty much the standard these days - most new installations are the "Darth Vader" hooded units.

Searchlights, which have one lamp and a movable interior mechanism to change colors, are fewer in number each year.

There was a model that had three separate lights inside a head that looked a lot like a searchlight.  Someone else can provide the model.

The B&O, PRR, and the like (position and color position) are in a class of their own.

Some heads have less than three lamps.  The signal for traffic northbound/westbound on the SW transfer at Deshler has three lamps in the bottom head, two in the middle, and only one at the top.

With the top head indicating track speed, it will never display anything other than red.  

The middle head has a red and either a lunar or amber/yellow.  I forgot to check it this past summer when I was there in person and you can't always tell on the webcams.  The lunar in the middle head would be restricting.

The bottom head has R/Y/G, indicating a slow speed movement.

The point here is that the heads will only have those colors that the signal can display.

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Posted by jeffhergert on Thursday, September 23, 2021 7:09 PM

Lithonia Operator

I see heads that have three lamps in them: green, yellow, red.

Is any more than one of the lamps ever lit at a time? I am thinking No, and that if you want green over yellow over red, you would need three heads. Correct?

 

Yes, only one light to a signal head at a time for the color light type.  If it's displaying more than one light, it's improperly displayed.  It is then regarded as displaying it's most restrictive indication possible.

Jeff

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Posted by Lithonia Operator on Thursday, September 23, 2021 8:07 PM

Thanks Jeff.

Still in training.


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Posted by blue streak 1 on Sunday, September 26, 2021 12:21 AM

Here on the A&WP sub CSX has changed somewhat.  The main line has several controlled sidings . The mainline exit masts have two heads.  All top heads have 4 bulbs with the 4th bulb a luna (white ) aspect.  Once the read of a train clears the CP the top head goes from red to Luna.  Once the rear of the train clears the next signal the head goes to yellow.  Once the train's rear clears the next signal the top head stays yellow and bottom head goes yellow ( call it advance approach ?) .  Next signal top head goes green and bottom goes back to red.

The sidings exit masts do not have this feature yet but have been told it is coming. They have top always red and bottom R, Y, G ?  

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Posted by tree68 on Sunday, September 26, 2021 7:35 PM

blue streak 1
The sidings exit masts do not have this feature yet but have been told it is coming. They have top always red and bottom R, Y, G ?  

The way I learned it is that there are "always" three heads.  A dark head is always the most restrictive aspect.  The missing bottom head would therefore be red, if there was one.  What you are seeing is the "middle" head, which would indicate a medium speed if they are using speed signalling.

The top head indicates track speed.  If track speed is never going to be seen there, it will always be red.

It's lunar - a bluish white, as opposed to white white.

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Posted by CSSHEGEWISCH on Monday, September 27, 2021 10:07 AM

White white indicated "clear" in the distant past and was eventually replaced by green for that indication.  Federal regulation eventually banned the use of white in signals which may be why lunar is used restricting indications. 

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Posted by cv_acr on Monday, September 27, 2021 10:40 AM

tree68
 

The way I learned it is that there are "always" three heads.  A dark head is always the most restrictive aspect.  The missing bottom head would therefore be red, if there was one.  What you are seeing is the "middle" head, which would indicate a medium speed if they are using speed signalling.

The top head indicates track speed.  If track speed is never going to be seen there, it will always be red.

Nothing is exactly that simple, however "diverging" indications usually have the green/yellow lights further down. So if there's no straight route, the top head will always be red.

The three head description above doesn't track reliably.

e.g. in Canadian speed signalling, on a three-head signal:

Green/red/red is Clear

Red/green/red is Medium to Clear

Red/red/green is Slow Clear

A two-head signal Red/green is Slow Clear. (equivalent to red/red/green. Green on the bottom is slow.) So that's kind of like the middle light being "missing". Compare aspects in Rule 431 and 422)

https://tc.canada.ca/en/rail-transportation/rules/canadian-rail-operating-rules/general-description-location-fixed-signals

But simple* "approach signals" like "Clear to Medium" (old name "Approach Medium") are Yellow/green or Yellow/green/red where the bottom head is dummy. (See Rule 407)

*There are alternate variations to this, and {reduced speed} to {reduced speed} indications get more interesting with Red/Green/Green indications for example.  (See Rule 418-420, 423-424)

There are (generally) some logical rules to go by in constructing indications:

  • Colour:
  • red is the most restrictive
  • if your system has lunar, it's less restrictive than red and more restrictive than yellow - generally reserved specifically for "Restricting" indications only. Many signal systems don't include lunar at all and use a yellow or blinking red.
  • yellow is less restrictive, and indicates a futher restriction at the next signal
  • green is least restrictive
  • a flashing light is less restrictive than a solid light of the same colour
  • the higher on the mast the non-red light is, the less restrictive. (top=clear, middle=medium or limited, bottom=slow or restricted)

It does get a bit wonky with more elaborate speed indications like Limited to Limited, etc. but it does still follow the pattern - blinky green (Limited) is better than solid green (Medium) is better than blinky yellow (Slow).

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Posted by tree68 on Monday, September 27, 2021 10:55 AM

B&O CPLs still use white for several of the markers.

 

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Posted by zugmann on Monday, September 27, 2021 10:59 AM

There are so many signal themes that were used be so many railroads all being merged and modernized in current times - you will go nuts trying to find some Rosetta stone to decipher it all as one.  

Easier to learn the signals of a certain territory/railroad/line that interests/is local to you. 

That being said - color LED position lights for the win. 

PS. we use "lunar white" for restricting and 'clear to next interlocking' signals here.  I don't know what makes it "lunar" other than name, but not worth worrying about.

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Posted by tree68 on Monday, September 27, 2021 1:19 PM

cv_acr
Nothing is exactly that simple,

True, but it's a start...

 

LarryWhistling
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Posted by BaltACD on Monday, September 27, 2021 7:05 PM

zugmann
There are so many signal themes that were used be so many railroads all being merged and modernized in current times - you will go nuts trying to find some Rosetta stone to decipher it all as one.  

Easier to learn the signals of a certain territory/railroad/line that interests/is local to you. 

That being said - color LED position lights for the win. 

PS. we use "lunar white" for restricting and 'clear to next interlocking' signals here.  I don't know what makes it "lunar" other than name, but not worth worrying about.

Wasn't there a derailment on the former Rock Island commuter territory with a former CSX engineer that had been hired to operate the Rock commuters - he confused the application of a signal that displayed the same lights, however it had a deadly difference in speeds allowed and he attempted to opeate his train at 45 MPH through a 10 MPH crossover with the expected results.  This happened on the order of 15 to 20 years ago.

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Posted by zugmann on Monday, September 27, 2021 7:10 PM

I remember the one wher an Amtrak crew confused a slow approach with a restricting and rear-ended a stack train about that time frame.  

 

I'm sure there were others.  PTC does help in this sort of thing. 

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Posted by jeffhergert on Monday, September 27, 2021 9:28 PM

The single always red over another signal head makes that a diverging signal.  The difference changes the indication.  The diverging indication is always going to have "not exceeding prescribed speed through the turnout" or similar language somewhere in it.

I see such signals more often at switches located at the end of two main tracks or other main track control points, not so much at the ends of sidings.  Possibly because they figure crews on trains leaving a siding are more aware of the switch they are going to use.  A crew running at speed on a track that ends on the diverging side of a turnout in case they have a momentary lapse.  I don't know.

PTC will eventually do away with signals altogether anyway.  Just ask the gung-ho PTC techies.Bang Head 

Jeff 

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