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Trackside signal heads and what they mean..?

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Posted by dehusman on Saturday, January 19, 2019 8:03 AM

OldEngineman
D&H is -entirely correct-

Just for the record, nothing in my post disagrees with D&H, it just gives a different perspective.

OldEngineman
I will assume that dehusman (being from Nebraska) is familiar with "west-of-the-Mississippi" rules and terminology, but perhaps less so with "eastern lines" such as the Pennsylvania, NYC, D&H, NHRR, etc.

I spent over 35 years in the operating department of a western road and the vast majority of that in the field or dispatch offices.

I do model an eastern road and do have many rule books from all over the country.  I model the RDG and fully admit they have a pretty unique rule book.

OldEngineman
This is why arguments and disagreements arise in a discussion topic like this, because the rules "ain't necessarily the same" from one railroad (or area of the country) and another.

And era.  Rules change over time.  I am modeling the 1900 era so its more obvious to me, but my professional career ran from train order operators copying flimsies with carbon paper to transmitting track authorities directly to trains and engines on computer screens.

The critical thing to understand is what are the rules/signals trying to do.  Pretty much most railroads are doing the same things, They just have different infrastructure to do it with.  Even the whole "route vs speed" signal debate isn't that much of a debate when you dig into it, both signals are trying to communicate to the crew that they will need to reduce the speed of a train to negoitate the alignment of the route over which it will be traveling.  

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Posted by jeffhergert on Saturday, January 19, 2019 12:07 AM

CTC, Centralized Traffic Control, was actually one of the signal supplier's name for it's brand of Traffic Control System.  Off hand I don't remember if it was US&S or GRS that had CTC.  Some railroads in the west also used TCS in their timetables and rules instead of CTC.  Eventually the use of the CTC name for any supplier's brand of TCS became common.

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Posted by OldEngineman on Friday, January 18, 2019 10:41 PM

There's something interesting regarding the posts of D&H Reitiree and dehusman above.

D&H is -entirely correct- in what he posted. He worked on the D&H (possibly under NORAC), I worked on Conrail, Metro-North, and Amtrak. For a time, we used NORAC as well (I think Amtrak still uses it on the Corridor). Metro-North has always had "their own book".

I will assume that dehusman (being from Nebraska) is familiar with "west-of-the-Mississippi" rules and terminology, but perhaps less so with "eastern lines" such as the Pennsylvania, NYC, D&H, NHRR, etc.

This is why arguments and disagreements arise in a discussion topic like this, because the rules "ain't necessarily the same" from one railroad (or area of the country) and another.

The term "TCS" (for "traffic control system") was in use for many years on Penn Central, Conrail, and MNRR. For all practical purposes, the operating principles it described were exactly the same as CTC -- PC just called it by a different name. In fact, not that many years back, they decided to change the name from "TCS" to "CTC". Nothing else was changed... except what they called it.

Even the behavior of certain portions of the railroad operating under TCS worked differently, depending upon where you were. For example, in Amtrak territory and former PRR territory, when the dispatcher set the direction of traffic for a particular direction, the signals would all "flop over" (i.e., clear in the direction set, red in the opposite direction).

Not so on former NYC territory. There (on the Hudson line, for example) the signals in TCS territory between interlockings would display "Clear" in BOTH directions regardless of how traffic was set. When you entered a section of territory between interlockings, it would "knock down" all the opposing signals in front of you to red, and you'd get clears ahead. But as soon as you cleared blocks behind you, they would go back to "clear" (for movement in the opposite direction).

I could be looking out the engineer's window behind, and watch the opposing signal behind me go from red to green and know that our rear end had just passed that point!

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Posted by dehusman on Friday, January 18, 2019 9:43 PM

D&HRetiree
Most of the comments I see here refer to TCS --Traffic Control System -- we did not use the term "cTc" as it is propietaty, used by a single manufacturer.

The term "CTC" is way more common on railroads, particularly western railroads, than "TCS". Checking the UCOR, CCOR (and a couple individual railroads) rule books post 1970's  they list rules for "Centralized Traffic Control" which is CTC.

On the MP/UP, TCS was the information computer system.  If you wanted info on a car or train, you looked in "TCS".   YMMV.

D&HRetiree
Single head signals are generally block signals and will have a number plate below the signal head.

On many roads they are called "intermediate" signals.

Distant (or approach) signals which immediately proced interlocking signals are generally two head and the heads are staggered-one on each side of the mast. (diffeent RRs stagger diferently).

Or not staggered.  Once again staggering the heads are typically eastern thing.  Western railroad don't generally stagger the heads and there is no differenciation in the rules regarding any stagger.

D&HRetiree
They also have number plates. Red block/distant signals can generally be passed after stopping but train must proceed at estricted speed until a more favoraable signal indication is passed.

 

Just to stir up some other mud, depending on the railroad and era, at a stop and proceed signal (typically a red signal with a number plate on the mast) a train must either :

  1. Stop and then proceed at restricted speed until it passes a more favorable signal.  If it encounters another stop and proceed signal it has to stop again then proceed.
  2. Stop and then proceed at restricted speed until it passes a more favorable signal.  If it encounters another stop and proceed signal it doesn't have to stop, it just proceeds at restricted speed
  3. Immediately reduce to restricted speed and pass the signal without stopping at restricted speed until it passes a more favorable signal.  If it encounters another stop and proceed signal it doesn't have to stop, it just proceeds at restricted speed
Option 3 on some roads is called a "restricting signal".  Which option applies depends on the era, the more modern the era, the more stop adverse the railroad is.
 
D&HRetiree
Interlocking signals are multiple head with the heads arranged vertically. They do not have a number plate and if red may only be passed with permission from the dispatcher.

Only if its a manual interlocking.  On an automatic interlocking, it could be a signal that has a single head, displays a stop indication (an abslolute signal) and the dispatcher cannot give a train permission to pass the signal.  At an automatic interlocking the crew can only pass a stop indication after complying with the instructions in the control box located at the interlocking itself.

Many rule books use the term "control operator" for the person incharge of an interlocking or CTC system.  While it is increasingly rare, the UP just retired its last manned interlocking tower, back in the day it was very common for an interlocking to be controlled by an operator in a tower and not by the dispatcher.  The tower operator worked for the dispatcher.  It was also very common for small islands of CTC to be operated by local "CTC operator" who was not a dispatcher, but worked for the dispatcher.  Lift bridges were the same thing, an operator.

 

 

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Posted by mbinsewi on Friday, January 18, 2019 9:35 PM

Well, the OP started a thread about Radio Shack, and well into the thread, he brings up his signal questions, I encouraged him to bring the signal isssue back here, or at least start another thread, as in the Radio Shack thread, he asked about powering a system, and what to use to control it.

I guess we'll see what happens.

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Posted by D&HRetiree on Friday, January 18, 2019 6:20 PM

Most of the comments I see here refer to TCS --Traffic Control System -- we did not use the term "cTc" as it is propietaty, used by a single manufacturer. When I was qualified as a track car operator TCS was explained to me as "Do what the signal says and don't back up without permission."

The number of "heads" used on a specific signal are dependent on how much information is to be conveyed to an approaching train.

Single head signals are generally block signals and will have a number plate below the signal head. Distant (or approach) signals which immediately proced interlocking signals are generally two head and the heads are staggered-one on each side of the mast. (diffeent RRs stagger diferently). They also have number plates. Red block/distant signals can generally be passed after stopping but train must proceed at estricted speed until a more favoraable signal indication is passed. Interlocking signals are multiple head with the heads arranged vertically. They do not have a number plate and if red may only be passed with permission from the dispatcher. Just to muddy the waters, A block signal with a "G" on a sign mounted below it becomes "Restricting" instead of "stop and proceed" These are used on ruling grades where a stopped train might not be able to re-start without assisstabce. A block signal with a "S" disk located at a passing siding would be a "Take Siding" indication in non TCS territory. The two head distant signals give the train operator information about the interlockubg signal ahead. 

Interloking signals are normally all red. After  the dispatcher sets the switches as desired, he clears the appropriate signal. He does not decide what the indication will be -- the signal system displays the signal indication based on switch position and local conditions.

Our RR used three head interlocking signal for consistency even if a two head signal would suffice. A non-red light in the top head meant the train was holding the main, a non-red light in the middle indicated the train would be taking a diverging route at a junction or passing track. A bottom yellow could mean the train was leaving TCS territory or that the track ahead was occupied or there was some other problem. This indication was also used to allow a helper to enter an occupied track so assist a train.

Don't know how much this helps--this is an instance where TMI" may apply.

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Posted by cv_acr on Monday, January 14, 2019 8:54 AM

Modern rulebooks (NORAC, GCOR, CROR, etc.) didn't just come out of nowhere and change the meaning of all the signals and make the railroads change them all. It's just an evolution and update of existing rulebooks and the signal information will simply carry forward from what was already in use. Most of the signal rules will be the same as decades-older rulebooks, and there are locations out there with 50+ year old original signals still in place still working as they did when first installed...

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Posted by dehusman on Monday, January 14, 2019 7:01 AM

ATLANTIC CENTRAL
I just got a little tired of "NORAC says.....", as if to imply that is the beginning and end of railroad signals. NORAC does not exist in my model world......

NORAC is derived in large part from the Penn Central rules which was derived in large part from the PRR rules.  The major difference in signal rules between a 1951 PRR rule book and a 2000 era NORAC rule book is they didn't have flashing aspects in 1951 (and there are a couple signals related to manual block in 1951 that didn't exist in 2000).

If you are reading NORAC you are more or less reading a PRR rule book.  That is a problem because the PRR, while it may have been called the "standard railroad of the world", was anything but standard with respect to the rest of the industry.

Even the PRR yard limit rule is different from virtually every other rule book.

You will also find that the Consolidated Code of Operating Rules (CCOR) is oft quoted in model railroad circles.  I can only think it was popular because many of the roads went through Milwaukee and that was Model Railroader's headquarters so that's what the MR guys had.

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Posted by ATLANTIC CENTRAL on Monday, January 14, 2019 4:38 AM

zugmann

 

 
ATLANTIC CENTRAL
Dave, you are the only person on "your side" of this discussion who does not seem to have an attitude towards us "lowly modelers" who are not real world railroaders. Have you read the unicorns profile page?

 

I don't think I ever gave an attitude towards any "lowly modelers".  If I have, please show me where?  I even dabbled in model trains (2 different gauges) a few times in my life (although not currently).

Second, it's actually an alicorn, not a unicorn.  Not that it matters, but my profile page?  In case we haven't formally met, I am zug, and I'm pretty much known for my warped humor.

 

I just replied with my approach slow since Jeff named what the signal is under his rulebook.  Nothing nefarious in it, no attempts to insult anyone, and I don't think I'm a higher being becuase I carry around a copy of NORAC.   Be a weird litmus test... would a demon carry GCOR? 

You do you... you can model whatever you want.  That's cool.

I look at this page from time to time since it is about protoype information for the modeler, and since I qualify for the first part, I share information.  Nobody has to read it or take it seriously if they don't want to. 

 

I'm sorry if that offended you.  My apologies, again.  

 

This thread has had a lot of missunderstood back and forth, and I am sorry if I included you with some others who seem to set themselves up as "experts" without understanding the context of this being the model railroad forum.

Again, my appolgies as well.

Sheldon

    

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Posted by zugmann on Sunday, January 13, 2019 11:06 PM

ATLANTIC CENTRAL
Dave, you are the only person on "your side" of this discussion who does not seem to have an attitude towards us "lowly modelers" who are not real world railroaders. Have you read the unicorns profile page?

I don't think I ever gave an attitude towards any "lowly modelers".  If I have, please show me where?  I even dabbled in model trains (2 different gauges) a few times in my life (although not currently).

Second, it's actually an alicorn, not a unicorn.  Not that it matters, but my profile page?  In case we haven't formally met, I am zug, and I'm pretty much known for my warped humor.

 

I just replied with my approach slow since Jeff named what the signal is under his rulebook.  Nothing nefarious in it, no attempts to insult anyone, and I don't think I'm a higher being becuase I carry around a copy of NORAC.   Be a weird litmus test... would a demon carry GCOR? 

You do you... you can model whatever you want.  That's cool.

I look at this page from time to time since it is about protoype information for the modeler, and since I qualify for the first part, I share information.  Nobody has to read it or take it seriously if they don't want to. 

 

I'm sorry if that offended you.  My apologies, again.  

 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 ATLANTIC CENTRAL on Sunday, January 13, 2019 4:22 PM

dehusman

 

 
ATLANTIC CENTRAL
Many of us who are interested in model trains have no interest or indepth knowledge of current prototype practice. Because many of us do not buy/build models of current trains.

 

 
ATLANTIC CENTRAL
So please excuse my lack of interest in your current railroading knowledge, I want to know more about signals from 70 years ago.

That's too bad.  The underlying concepts are pretty much the same as they were 100 years ago.  

I would give you some examples, but I don't want to distract you with "modern stuff."

 

Dave, you are the only person on "your side" of this discussion who does not seem to have an attitude towards us "lowly modelers" who are not real world railroaders.

Have you read the unicorns profile page?

I understand everything you have explained, and most I already understood. 

My point remains, a point you have made repeatedly as well from your prespective, signaling cannot be boiled down to a few simple "rules". 

It is complex, its history in North America is long and complex, its applications today and in the past are complex.

I just got a little tired of "NORAC says.....", as if to imply that is the beginning and end of railroad signals. NORAC does not exist in my model world......

I have been considering a reply to the earlier part of thread in which you tried to explain to Ed about the application of signal indications and rules.

You are right, very few rule books make any reference to turnouts or diverging routes regarding particular signal aspects.

BUT, from the other side, from the seat of the guy who designs the system, the guy who figures out the relay logic to control those lights, a truth table of questions must be written for each signal head individually.

And if a turnout, or multiple turnouts are involved, those are the first pieces of information in the chain for the top head on the mast, for any given track.

If a trailing point turnout is set against that track, that top head will be red, unless there is a facing point turnout before that set to put the train on a different route. And if not, they all better be red......

From the system designers standpoint, the typical control point or interlocking, particularly with CTC, does often relate the top head to the main route, the second head to the next route, and the third head to the route beyond that, etc.

Yes, they may be cross interlocked to provide special indications, but the design process starts there.

I have studied prototype wiring diagrams, I have studied and designed relay based model systems.

That might not be how we want train crews to read them, but it is largely how the aspects are created on an equipment level as it relates to junctions, crossovers, diverging routes that are signal controlled.

The final two links in the chain are "is there a train in front of me on the route I have been given?", and if it is CTC, "did the dispatcher say I could have the route?".

After all that the relays and track circuits will give me that magic selection of colored lights that fit the situation, and it is my job to control my train accordingly.

But as a modeler, not all of us want to just wire inputs and outputs to a logic device (computer, PLC, etc) and rely on software someone else created to get aspects someone else told us were correct.

Some of us want to understand why that track/route/occupancy/authority chain created that set of aspects.

For which I would refer anyone to Bruce Cubb's first signal system published in MR, or Ed Ravenscoft's MZL control.

Sheldon

 

 

    

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Posted by dehusman on Sunday, January 13, 2019 12:47 PM

ATLANTIC CENTRAL
Many of us who are interested in model trains have no interest or indepth knowledge of current prototype practice. Because many of us do not buy/build models of current trains.

ATLANTIC CENTRAL
So please excuse my lack of interest in your current railroading knowledge, I want to know more about signals from 70 years ago.

That's too bad.  The underlying concepts are pretty much the same as they were 100 years ago.  

I would give you some examples, but I don't want to distract you with "modern stuff."

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Posted by zugmann on Sunday, January 13, 2019 12:18 PM

ATLANTIC CENTRAL
So please excuse my lack of interest in your current railroading knowledge, I want to know more about signals from 70 years ago.

 I apologize for making a comment on here.   How silly of me.

 

 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 ROBERT PETRICK on Sunday, January 13, 2019 10:33 AM

mbinsewi
ATLANTIC CENTRAL
And here in lies the problem with discussing prototype railroad signaling practice on a model railroading forum.

As I've learned, from this thread and others.  Just too much information, some of it conflicting.

I have NO club experience.  How does a club handle signaling?  I'm guessing they come up with some kind of an SOP, so everyone who operates on it is on the same page.

But I don't know.

Mike.

I can tell you how my previous club handled signaling . . . they talked about it. That was fifteen years ago. I bet they're still talking about it.

Robert 

LINK to SNSR Blog


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Posted by mbinsewi on Sunday, January 13, 2019 10:07 AM

ATLANTIC CENTRAL
And here in lies the problem with discussing prototype railroad signaling practice on a model railroading forum.

As I've learned, from this thread and others.  Just too much information, some of it conflicting.

I have NO club experience.  How does a club handle signaling?  I'm guessing they come up with some kind of an SOP, so everyone who operates on it is on the same page.

But I don't know.

Mike.

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Posted by ATLANTIC CENTRAL on Sunday, January 13, 2019 9:28 AM

zugmann

 

 
jeffhergert
On the Union Pacific it's called approach diverging. May be called and mean something different on another railroad.

 

We call it approach slow on Norac-type places.

 

And here in lies the problem with discussing prototype railroad signaling practice on a model railroading forum.

Many of us who are interested in model trains have no interest or indepth knowledge of current prototype practice. Because many of us do not buy/build models of current trains.

On my little railroad, it is always September 1954, long before the creation of NORAC in 1985.

And I even control my little signals with relay circuits almost identical to those used on the big railroads in 1954.

What is going on with that rusty, graffitti covered mess that passes for railroading today is of little interest to me.

And I may not have any real world experiance working on the prototype, but my son does, and so do a number of my friends........

So please excuse my lack of interest in your current railroading knowledge, I want to know more about signals from 70 years ago.

Sheldon

    

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Posted by zugmann on Saturday, January 12, 2019 10:03 PM

jeffhergert
On the Union Pacific it's called approach diverging. May be called and mean something different on another railroad.

We call it approach slow on Norac-type places.

 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 dehusman on Saturday, January 12, 2019 9:44 AM

mbinsewi
Would there have been some 5' or more, track gauges back then?

Most of the lines were "standard gauged" by the mid 1890's.  Most of the 5 ft gauge lines were in the south and west.

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Posted by mbinsewi on Saturday, January 12, 2019 9:39 AM

Dave, sounds like an interesting modeling adventure.

Would there have been some 5' or more, track gauges back then?

It looks like the OP has decided not to join in any of this.  As usual.

Mike.

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Posted by dehusman on Saturday, January 12, 2019 9:20 AM

jeffhergert
That's why when talking about specific signals one needs to specify railroad and even era (year).

On the railroad I'm modeling, in 1900, signals would have been white for clear, green for caution and red for stop.  In 1903,  signals would have been green for clear, yellow for caution and red for stop. 

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Posted by CGW121 on Saturday, January 12, 2019 7:16 AM

jeffhergert

Also in the case of larger railroads that have aquired several other railroads, you can have different rules on different districts. Its not a quessing game thats part of being qualified on a route

 

 
CGW121

Yellow over yellow: advanced divirging  rule 235 Wisc Central rr rule book 1998. I saw a friend last evening. He was a yardmaster with the UP for at least 10 years. He knew what it meant and what rule it is on the UP. Point is if you want to know ask the guy who works with it for a living. 

 

 

 

 

 

On the Union Pacific it's called approach diverging.  May be called and mean something different on another railroad.  That's why when talking about specific signals one needs to specify railroad and even era (year).

Jeff

 

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Posted by jeffhergert on Friday, January 11, 2019 11:47 PM

CGW121

Yellow over yellow: advanced divirging  rule 235 Wisc Central rr rule book 1998. I saw a friend last evening. He was a yardmaster with the UP for at least 10 years. He knew what it meant and what rule it is on the UP. Point is if you want to know ask the guy who works with it for a living. 

 

 

 

On the Union Pacific it's called approach diverging.  May be called and mean something different on another railroad.  That's why when talking about specific signals one needs to specify railroad and even era (year).

Jeff

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Posted by CGW121 on Friday, January 11, 2019 7:56 AM

Yellow over yellow: advanced divirging  rule 235 Wisc Central rr rule book 1998. I saw a friend last evening. He was a yardmaster with the UP for at least 10 years. He knew what it meant and what rule it is on the UP. Point is if you want to know ask the guy who works with it for a living. 

 

 

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Posted by jeffhergert on Wednesday, January 9, 2019 6:26 PM

Where I work, there is one location (a junction point) where the best signal possible is a red over green no matter if you're going straight or on the diverging route.  The top light is a dummy, constantly lit red light.  The reason being that the straight route joins one of the mains coming into the junction, going through the diverging portion of that turnout.

A signal with a constant red light on top, making all signal indications being a "diverging" signal are not unusual.  The ones I'm familiar with are at locations where a main track ends or joins another main track and trains using that route are going through the diverging portion of the turnout.  

Jeff

 

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Posted by cx500 on Tuesday, January 8, 2019 11:24 PM

Where speed signalling is the method of operation (probably the most common in North America), the signal at the entrance to the siding is used to convey two separate pieces of information.  The most immediate item is the position of the switch (normal, reversed, or out of register).  If the latter it had better be red!  Second is allowable speed through the turnout depending on its geometry.

The second is occupancy of the track on the selected route beyond, IF KNOWN.  While the main track will almost certainly have track circuits, as a cost saving measure the siding may be unbonded, hence dark territory.  As others have been insisting, it is the combination of the two (or three) heads that convey the full meaning.

For the simple situation of a passing siding on single track main line, the signal indications do superficially resemble how the OP has interpreted them, but the logic is a lot more complicated.

And in the category of exceptions, at one junction I am aware of, the clear signal was for the diverging side of a turnout since that was the the alignment of the subdivision.  Tracks 1 and 2 were 50 mph (no turnout) and Track 3 was 25mph because of that turnout.  Shown in the employees timetable, not by signal indication.  Straight through on the turnout had a more restrictive indication, probably mostly due to following parts of the route.  It snaked across two double track main lines before joining another subdivision on the diverging side of a turnout. 

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Posted by dehusman on Tuesday, January 8, 2019 10:22 PM

ATLANTIC CENTRAL
Dave, I understand, but Ed is just talking about that one isolated example, a two head signal located at (lets assume just before) a siding.

The hypothesis that has been put forward that Chris and I are discussing is that on a two headed signal, the top head indicates the condition of the main track and that the bottom signal indicates the condition of the siding.  

In the very limited example of a siding, when the switch is lined for the main, the top head may have a color other than red.  When the switch is lined for the siding, the bottom head may have a color other than red.  However that still doen't prove the hypothesis because there are dozens of examples of signals with two heads at other places that don't follow that logic, you can have two heads and not have a siding.  There are NO signal indications that say anything about a siding.  There are no rules that tell a crew to interpret signals that way.  I've taught rules classes to trainmen and that's not how it was taught.

If somebody wants to use that as a rule of thumb in the one and only one case of a signal approaching a siding, restricting to just those 4 signal indications, just on route signals, they will probably get the gist of the signal right.  However if they try to translate that logic to other signals, it ain't going to work.  

Why create a special case exception that only works in one specific circumstance?  Just do it right the first time.

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Posted by ATLANTIC CENTRAL on Tuesday, January 8, 2019 8:15 PM

Oh yes, and then there is the difference between an interlocking and a control point......

OK, I'm getting bored, back to drawing the new layout plan......

Sheldon

PS - ok, one last question for Dave or others, I know Dave has real world experiance in the Cab, does Dave (or others) have knowledge of how relays (back in the day), along with the track circuits, generated all these complex aspects? (I do, my first job as a "grown up" envolved designing complex relay circuits, later I converted relay circuits into PLC logic....)

    

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Posted by ATLANTIC CENTRAL on Tuesday, January 8, 2019 8:01 PM

dehusman

 

 
7j43k
So. Tell me. What are the circumstances that would generate a yellow over yellow for the plain ole siding described above. Remember. YOU'RE the guy who is asserting it can happen. Not me. So........

 

Very simple.

Lets use the 1980 BN signal rules in the CCOR.

Yellow over Yellow.  Rule 501A.  Proceed prepared to stop at the second signal.

Its probably territory with a 60-79 mph max speed.  Both siding switches lined for main.  Next signal does not display not stop.  Signal after that displays stop.  Both blocks to the stop are not occupied.

That wasn't that hard was it?

Now I have a couple questions for you.  You assert that the top signal indicates the condition of the main track and the bottom signal indicates the condition of the siding.

On single main track, no siding for 10 miles, there is a two headed signal that displays yellow over yellow.  If the bottom signal pertains to the siding, how does it display yellow over yellow if there is no siding?

At a location there is a siding on both sides of the main track (east siding and west siding).  The signal approaching one end displays diverging approach, red over yellow.  To which siding does the signal apply and how does it apply when one siding switch is lined for the main and one is lined for the siding?

At the end of a siding, where the track goes from a main and a siding to a single main, the LEAVING signals have two heads.  Once again, if the lower signal head pertains to the siding, why is there a lower head when beyond the switch there is no siding, only single main?

 

 

I knew this was headed here next, exactly my point earlier, too many facts not in evidence.

Dave, I understand, but Ed is just talking about that one isolated example, a two head signal located at (lets assume just before) a siding.

I also understand, we cannot assume that every railroad, in every era, even with the same general operating conditions, would signal that siding the same way.

For some railroads, in some eras, on some systems, Ed would be correct, and one head would always be red.

This whole discussion is a prime example of why we do not need truely prototypical signals on our model layouts.........

And why it has taken decades for the rail industry to start to standardize signal practice.

Real railroads deal with hundreds of miles of varied operating conditions, we are a lucky if we are dealing with hundreds of feet.........or a handful of scale miles.

For those without prototype experiance, the variations can be a lot to learn about and absorb. It took me while and still don't have your kind of knowledge, even with my son being an Engineer.......

But I know enough to understand just how much more there is for me to know, and I know enough to make my model system look realistic and function well.

I suspect Ed may be on a similar journey.

Yellow over yellow is a speed/occupancy aspect, not a route control aspect.

And there is the complext part, some signals are speed/occupancy only, some include route control/indication, some permissive, some are absolute, all tell the engineer what he should be prepared for next........but you already know all this.....

Sheldon 

    

  • Member since
    September 2003
  • From: Omaha, NE
  • 9,588 posts
Posted by dehusman on Tuesday, January 8, 2019 7:41 PM

7j43k
Did BN not have flashing yellow in 1980?

Yes they had flashing signals, but for different indications.

7j43k
The discussion is only about a passing siding. So this doesn't apply. Sounds like it's speed signaling, though.

There are no "these are just for sidings" signals.  The indications apply the same wherever they are displayed.

7j43k
It applies to the route through the interlocking. I am presuming there are three signals at the other end of the interlocking, right?

Its not an interlocking, its the end of a station with a siding on either side of the main, a control point just like anyother control point a the end of a station with a single siding.  There would be a leaving signal on each siding and on the main.

7j43k
Because there is, at this location, a need to give the engineer more information than a single head can. And, therefore, this is not the "simple siding" that I am referring to.

But its the same signal, its the same aspect, its the same indication, it has the same requirements, there is absolutely no difference in the rules based on the location, whether there is a siding or there is not a siding.

If the same signal is displayed whether or not there is a siding, whether or not the siding is occupied, then that would be pretty rock solid case that the lower signal head doesn't "belong" to the siding.

The signal indication is based on the overall condition of the tracks and the switches in the route.  The upper signal is NOT tied to the main and the lower signal is NOT tied to the siding.  The signal system does not figure out the top head, then figure out the bottom head, the signal head doesn't decide what to display. If figures out the indication for the entire signal  and you read the whole signal, all together.

We are right back where we started.

Dave H. Painted side goes up. My website : wnbranch.com

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