CTC Control Point

[JWB]

Here is the westward signal at CP Jaques (note spelling -- pronounced "JAY-kweez", named for pioneer US model railroader and nature painter F.L.Jaques) on my layout. It is one of the fairly recent NJI "Darth Vader" signals, which I know for sure are used on BNSF and CSX, likely others.

With the switch in the normal position, the top indication is green, the bottom red.

With the switch in the reverse position, the top indication is red, the bottom green.

When the OS section is occupied, both heads are red.

I'm doing this with analog DC. Some of the circuits, mainly Radio Shack relays and Dallee Electronics detectors, are shown here. I'm "spoofing" the operation of CTC, as the wiring for a full board is more than I want to tackle, and the politics of putting enough operators together to justify it is also more than I want to take on.

 

You will notice there is a switch heater in the scene. I'm adding these where appropriate with the Details West kits. I'm having a hard time finding good info on switch heaters -- for instance, I don't know who manufactures the prototype for these, what the era is, etc. However, I did find a somewhat similar one while passing thru Kansas City a couple of years ago on the Southwest Chief:

[Prof Klyzlr]

Dear JWB,

 

a quick Google turned up

 

http://www.tflexsys.com/this_railroad_switch_heating_sys.html

 

 

 

http://www.freepatentsonline.com/3697746.html

(no pics, but an interesting read)

 

 

 

http://www.railsco.com/

Useful, particularly

http://www.railsco.com/~rail-tel_rts_switch_heater.htm

 

 

 

http://www.patentstorm.us/patents/4195805/description.html

Again, no pics but more info...

 

 

 

Even Model Trains need switch heaters...

http://www.adaptivethermal.com/products/consumer/train.html

 

 

Hope this helps...

 

Happy Modelling,

Aim to Improve,

Prof Klyzlr

[signalmaintainer]

Nice look to the scene! The Diverging Clear aspect for the switch lined reversed is spot on!

 

The propane-fired switch heaters and top-mount signal bungalows are pretty contemporary, as far as era goes. We typically use the top-mounts at distant and intermediate signal locations. The cases measure only 4x6 feet, and there's not enough room in them for the batteries, chargers, processors, relays, local control panel and other appartus needed for a control point. However, there's a prototype for everything!

[JWB]

Actually, the NJI configuration had me puzzled. Two heads directly over each other would, at least in earlier times, mean an absolute signal. This may have changed. NJI puts a milepost plate on it as it comes, which wouldn't normally be consistent with an absolute, according to my understanding, so I dremeled it off.

 

I'm pretty sure I saw one like this at a crossover on the BNSF double-track line between Galesburg and Aurora. I don't know what other stuff they had in the immediate area, though, as the Southwest Chief was moving along.

[dave1905]

Nice look to the scene! The Diverging Clear aspect for the switch lined reversed is spot on!

 

Assuming he is lining a train into a siding to make a meet and there are no intemediate signals in the siding, wouldn't the signal actually display diverging approach?

 

Proceed on diverging route prepared to stop at the next signal, not exceeding 30 mph.

 

Diverging clear implies the next signal is better than stop. If he is making a meet, then the next signal, the other end of the siding, would be stop.

[signalmaintainer]

Assuming he is lining a train into a siding to make a meet and there are no intemediate signals in the siding, wouldn't the signal actually display diverging approach?

 

Proceed on diverging route prepared to stop at the next signal, not exceeding 30 mph.

 

Diverging clear implies the next signal is better than stop. If he is making a meet, then the next signal, the other end of the siding, would be stop.

 

I see your point, Dave. If the train was being lined into a CTC siding to clear another train, the Diverging Approach aspect would be appropriate.

 

However, when a single-track main diverges into two main tracks, as could be the case here (and in real life examples such as MP 18 on BNSF's Scenic Subdivision), a Diverging Clear would be an appropriate aspect.

[JWB]

Here's the nature of the model railroad universe: CP Jaques is somewhere in the upper Midwest, possibly in DMIR or maybe BN territory. The other end of the siding, CP Loma, is about 20 track feet away, on the other side of a tunnel, in territory that is almost certainly SP or WP in northern California. (Signals there are still being installed; this is not the CP itself, but the general area.)

This is because it's my layout and I'm doing it my way. Given the theoretical distance, we may assume there are many, many intermediate signals between the two control points.

 

More seriously, I'm trying to take advantage of available commercial products that appeal to me and get things done in one lifetime. Had I found a signal that I liked that had a diverging approach aspect, I would have used it. If I find one in the future that does, I may well replace this one, but frankly, I like this one a lot. All I would need to do would be connect the wire for the yellow aspect at the lower head where the green one is connected now.

[JWB]

Giving this some more thought: the working railroaders may be able to correct me or clarify things here, but as I understand it, having been around the block enough times to know that there are many gotchas in life, "CTC" is a general term referring to certain operating rules whereby a dispatcher controls trains by signal indication, eliminating in part the need for train orders or track warrants. However, and here's the gotcha, I don't believe saying "CTC" immediately implies the use of certain signal indications in all circumstances.

 

A couple of years ago I ran into an ICC accident report on the web (can't remember where), which I found surprising because it had a big gotcha. It turns out that a wreck occurred because a train was routed onto a siding via a CTC signal indication at a control point, under CTC rules. BUT, GOTCHA, the "CTC" siding didn't have a circuit! So the siding was occupied, but the CTC signal at the control point didn't indicate this, because there was no track circuit in the siding to tell the signal this! My memory of the report is that the indication was "diverging clear", which would be logical if no circuit was issuing a code to cancel the clear.

 

I assume it was pretty unusual to have a CTC siding without a circuit, but obviously not unheard of. I don't know if the ICC then required CTC sidings to have circuits afterward or not, for that matter. But it appears that it was at least at one time possible to say there was CTC in effect, but a siding could get away with not having a circuit, and it would then apparently have been possible to have a diverging clear aspect on an ordinary controlled siding.

 

For that matter, John Armstrong mentioned in one of his books a "poor man's CTC" that was installed on some railroads like the WP, where the dispatcher and control points only governed traffic in one direction. (Again, I may not be clear on this, and a working railroader may be able to correct or clarify this.) It seems to me this could also affect the signal indications you might see under CTC. So I'm not sure that the term CTC refers to something clearly defined in every case.

[signalmaintainer]

Giving this some more thought: the working railroaders may be able to correct me or clarify things here, but as I understand it, having been around the block enough times to know that there are many gotchas in life, "CTC" is a general term referring to certain operating rules whereby a dispatcher controls trains by signal indication, eliminating in part the need for train orders or track warrants. However, and here's the gotcha, I don't believe saying "CTC" immediately implies the use of certain signal indications in all circumstances.

 

You understand the principle : In CTC, signal indication is the authority a train requires to proceed into the next block, rather than requiring a track warrant. Not all control points are designed so that the signals will display all the available range of signal indications.

 

A couple of years ago I ran into an ICC accident report on the web (can't remember where), which I found surprising because it had a big gotcha. It turns out that a wreck occurred because a train was routed onto a siding via a CTC signal indication at a control point, under CTC rules. BUT, GOTCHA, the "CTC" siding didn't have a circuit! So the siding was occupied, but the CTC signal at the control point didn't indicate this, because there was no track circuit in the siding to tell the signal this! My memory of the report is that the indication was "diverging clear", which would be logical if no circuit was issuing a code to cancel the clear.

 

I assume it was pretty unusual to have a CTC siding without a circuit, but obviously not unheard of. I don't know if the ICC then required CTC sidings to have circuits afterward or not, for that matter. But it appears that it was at least at one time possible to say there was CTC in effect, but a siding could get away with not having a circuit, and it would then apparently have been possible to have a diverging clear aspect on an ordinary controlled siding.

 

For that matter, John Armstrong mentioned in one of his books a "poor man's CTC" that was installed on some railroads like the WP, where the dispatcher and control points only governed traffic in one direction. (Again, I may not be clear on this, and a working railroader may be able to correct or clarify this.) It seems to me this could also affect the signal indications you might see under CTC. So I'm not sure that the term CTC refers to something clearly defined in every case.

 

In CTC territory, every block has a signal governing entrance into it, and every block has one or more track circuits.

In a nutshell, CTC is a series of manual interlockings (control points remotely operated by a dispatcher) separated by blocks governed by automatic block signals (intermediates, not under control of the dispatcher), with CTC rules applying throughout.

 

The definition of CTC, according to the Federal Railroad Administration, is, "A block signal system under which train movements are authorized by block signals whose indications supersede the superiority of trains for both opposing and following movements on the same track."

 

"Poor Man's CTC" is an informal term with more than one definition. For example, it can be a system that utilizes non-signaled territory interspersed with islands of CTC control points. When the train is in dark territory, it's governed by Track Warrant rules and requires a track warrant for authority to proceed. There are no intermediates between control points; rather, trains encounter distant signals in approach to control points. While in CTC sections, CTC rules apply.

 

I've heard other types of operation described as Poor Man's CTC, such as Double Track ABS. I can't describe them as I have no practical experience with them. Seems as if every railroad back from the 1950s through the early 1990s had a peculiar version of PMCTC.

[BR60103]

CTC means Centralized Traffic Control. Local signalboxes have been removed. CTC is not universal: there are lines that are called "dark territory" with no signals at all.

There seem to be at least 2 sets of signal meanings (in the US). I posted pages from the Canadian rule book (the obsolete one) showing our version -- the interpretation is similar to yours.

Our local shortline has a crossing with one mainline railway and a junction with the other (its former parent) and these are the only places it has signals as it operates on one engine in steam.

[dave1905]

"CTC" is a general term referring to certain operating rules whereby a dispatcher controls trains by signal indication, eliminating in part the need for train orders or track warrants. However, and here's the gotcha, I don't believe saying "CTC" immediately implies the use of certain signal indications in all circumstances.

 

CTC supercedes superiority of trains and signal indication authorizes movement (classic definition) or where the signal indications authorize movement (modern definition).

 

Even in CTC every train gets at least one track warrant, a warrant for bulletins, which is essentially the same as a clearance in old train order days.

 

A couple of years ago I ran into an ICC accident report on the web (can't remember where), which I found surprising because it had a big gotcha. It turns out that a wreck occurred because a train was routed onto a siding via a CTC signal indication at a control point, under CTC rules. BUT, GOTCHA, the "CTC" siding didn't have a circuit!

That's not a "gotcha". There is no requirement that sidings be bonded. It isn't at all uncommon to have unbonded sidings, especially on older sections of the railroad.

 

So the siding was occupied, but the CTC signal at the control point didn't indicate this, because there was no track circuit in the siding to tell the signal this! My memory of the report is that the indication was "diverging clear", which would be logical if no circuit was issuing a code to cancel the clear.

Actually that wouldn not be logical, the best signal you should get into an unbonded track is a low/restricting/slow type signal, but not a diverging clear. The siding would also be indicated in the timetable as not being bonded (technically most timetables list or denote the sidings that ARE bonded.)

 

I assume it was pretty unusual to have a CTC siding without a circuit, but obviously not unheard of.

It was not unusual. Since you mentioned the WP, most sidings on the former WP have a lunar (restricting) as the best signal entering the siding.

 

I don't know if the ICC then required CTC sidings to have circuits afterward or not, for that matter.

Since there are still unbonded sidings I don't think there was any such ruling.

 

But it appears that it was at least at one time possible to say there was CTC in effect, but a siding could get away with not having a circuit, and it would then apparently have been possible to have a diverging clear aspect on an ordinary controlled siding.

Still is possible to have an unbonded siding. The signal should be a lunar into the siding.

 

For that matter, John Armstrong mentioned in one of his books a "poor man's CTC" that was installed on some railroads like the WP, where the dispatcher and control points only governed traffic in one direction. (Again, I may not be clear on this, and a working railroader may be able to correct or clarify this.) It seems to me this could also affect the signal indications you might see under CTC. So I'm not sure that the term CTC refers to something clearly defined in every case.

 

Yes it is clearly defined. Read a rule book. CTC is intended to authorize movement on the main track. Just because you have different signal indications doesn't mean its not CTC. If you are authorizing movement in using signal indications then and the dispatcher controls which signals are cleared, its CTC. In some cases "poor man's CTC" only controls the signals and switches at one end of a siding, The other end is a spring switch. Its still CTC.

[dave1905]

Local signalboxes have been removed.

Depending on what you mean, maybe sorta no. In N America a "signalbox" is a cabinet next to the tracks full of relays and signal circuits. Those "signal boxes" are still very much in use.

 

If you are using the UK term of signalbox, a manned location that controls signals, then its sorta maybe. There are still a few locations where there are "control operators" that run CTC panels. There were hundreds of those locations several decades ago, many fewer now.

 

CTC is not universal: there are lines that are called "dark territory" with no signals at all.

 

Sorta maybe.

It boils down to control of the main track.

Authority on the main track can be granted by:

Schedule

Train order

Track warrant

Block authority (manual block or DTC)

Signal indication.

 

Schedule, train order, track warrant or block authority can be either dark (no block signals) or have an ABS block signal system overlaid. None of these are CTC.

 

Double track rule 251/rule 9.14 territory is an ABS system where the trains move with the current of traffic, signal indication supercedes superiority of trains and grants authority on the main track. This is not CTC.

 

Then there is CTC, where signal indication supercedes superiority of trains and grants authority on the main track, and the dispatcher controls the signals.

 

There seem to be at least 2 sets of signal meanings (in the US). I posted pages from the Canadian rule book (the obsolete one) showing our version -- the interpretation is similar to yours.

Our local shortline has a crossing with one mainline railway and a junction with the other (its former parent) and these are the only places it has signals as it operates on one engine in steam.

The signals have the same meanings, they just have different applications. The crossing is an "interlocking" which is another type of signal system. An interlocking can be either automatic (controlled by signal circuits) or manual (controlled by a human operator).

[JWB]

Paul and Dave, thank you very much for your clarifications. Paul's comments help me to understand something I saw on the CN ex-DMIR driving west of Duluth: when you come to the OS section governing a CTC siding, there's a sign on the mast of the signal facing the single track saying BEGIN CTC. Then, 150 feet or whatever farther along, on the masts of the signals ending the siding-and-main section (which are facing the other direction, but the signs are still facing the single track), there are signs saying END CTC. So the CTC rules here apply only to the 150 feet of the OS section. I think there are distant signals on the single track before the OS section, but no other intermediates. Dave is certainly right in saying that CTC means using signal indications to override certain other conditions, but in a case like the former DMIR, the CTC applies in 150 foot increments every few miles. So it seems to me still that CTC can mean different things in context, including what happens if a siding isn't bonded -- and I'm interested to learn this isn't all that uncommon. And I note Dave uses "should" a lot with what signal indications may apply to these situations. What should be, I would say based on some decades of experience with how things are, isn't necessarily what is!

[dave1905]

Paul's comments help me to understand something I saw on the CN ex-DMIR driving west of Duluth: when you come to the OS section governing a CTC siding, there's a sign on the mast of the signal facing the single track saying BEGIN CTC. Then, 150 feet or whatever farther along, on the masts of the signals ending the siding-and-main section (which are facing the other direction, but the signs are still facing the single track), there are signs saying END CTC. So the CTC rules here apply only to the 150 feet of the OS section.

That was really common on the SP also, having little CTC islands. That allows the dispatcher to control the siding switch so it can support cabooseless operation and can provide some of the control of CTC without the expense of full CTC. Many times the other end of the siding is a spring switch.

 

Dave is certainly right in saying that CTC means using signal indications to override certain other conditions, but in a case like the former DMIR, the CTC applies in 150 foot increments every few miles. So it seems to me still that CTC can mean different things in context, including what happens if a siding isn't bonded.

CTC authorizes movent by signal indication. It means exactly the same thing in this case, the signal indication authorizes movement past the CTC signal. The only thing a bonded siding has to do with it is what the most favorable indication the signal will convey.

 

And I note Dave uses "should" a lot with what signal indications may apply to these situations. What should be, I would say based on some decades of experience with how things are, isn't necessarily what is!

Because there are many different uses for signals and many different situations, different rule books over 75 years of evloving technology, communication and regulations, it is always possible to come up with an exception or a unique situation. So unless you specify an era and a railroad or rule book, the answers will be qualified. Generic questions get generic answers, and they have "should" and "could" a lot in them. 8-)

[JWB]

^{I think this goes again to the odd question of what "CTC" really means. As Paul suggests, there were many flavors. One thing that was common, as far as I can tell, was to replace old mechanical interlockings with small CTC machines located in the old tower building. The Philip Hastings Rock Island book illustrates one of these, for instance. However, they controlled nothing more than the area of the former mechanical interlocking, or maybe just added another one a couple miles down the line. For that matter, the PRR had a very bad head-on between a freight and a gas-electric in Ohio in the 1930s that was caused by the gas-electric crew screwing up on what was a sort of honor system manual block control. The PRR was forced by the ICC to replace this with CTC, probably because it was current technology. So there were little "islands" of CTC all over, for various different reasons.}

[dave1905]

CTC and manual interlocking rules are almost exactly the same since they are basically the same thing, a location where a person controls the route choice and clears the signals, and the authority to move is conveyed by signal indication which supersedes the superiority of trains.

 

I see no difference in a CTC section that is 150 feet long and one that is 150 miles long. The rules will be the same, the signal indications mean the same thing (although different indications may be given) and the purpose is the same (to grant authority by signal indication).

 

If a train comes up to a CTC signal, the train will do the exact same thing the indication tells him to do regardless if the CTC extends 150 ft beyond the signal or 150 miles beyond the signal. If the signal is red, the exact same rules apply to pass it regardless how far the CTC extends. If the train has to make a reverse move between outer opposing signals at the control point, the same rules apply.

 

What is different isn't the CTC, what's different is what's between the control points. Don't confuse the two. So yes, little islands of CTC were pretty common, but it was the same CTC rules wherever it was on a particular railroad.

[JWB]

Well, yes, a red is a red, though even on a 1988 UP employee timetable at http://www.lundsten.dk/us_signaling/aspects_up1988/index.html you might say a red is "all of the above". And that doesn't include the ex-B&O color position light signals that the UP inherited with the SP/Gateway Western merger in 1995!

 

My guess is that even on the same railroad in the same time period, you'll find a goldmine of exceptions and special cases in the special instructions! Just sayin!

[dave1905]

But one red lens in a signal doesn't make it the same as all aspects with a red lens, its the combination of colors and their position relative to each other. One combination is one and only one indication. There is no aspect that has two indications. There are many combinations, but each combination has one and only one meaning. You are making this way harder than it is.

[JWB]

Here's how I see it. There are working railroaders who seem to think those who haven't passed a rules exam are unworthy. I know several. They'd probably flunk any rules exam not given by their favorite examiner. There are other working railroaders who say to those guys, "Geez, don't you get enough of that at work?" There are modelers and railfans who don't have to pass a rules exam who say, "Wow, if you take this really, really seriously, especially if you don't have to bluff your way past a single rules examiner, this is a really, really complex subject, and I'm happy with sorta-kinda, since my next project is wondering whether I can get a 1944 AAR boxcar for the xyz railroad superdetailed with just Joe Blow's kit, or if I have to kitbash it using a Balderdash as well." Each to his or her own!

[signalmaintainer]

Well, yes, a red is a red, though even on a 1988 UP employee timetable at http://www.lundsten....1988/index.html you might say a red is "all of the above". And that doesn't include the ex-B&O color position light signals that the UP inherited with the SP/Gateway Western merger in 1995!

 

My guess is that even on the same railroad in the same time period, you'll find a goldmine of exceptions and special cases in the special instructions! Just sayin!

 

JWB, a red in a signal aspect isn't always treated as "red trumps all." The interpretation is based on the entirety of the aspect and what that aspect indicates, not just whether that aspect has a red in it. (There aren't that many exceptions in the Special System Instructions.)

 

For example, on the BNSF, the aspects Red over Green, R/Flashing Yellow, and R/Y do not indicate stop. Rather, they indicate that a train will be taking a diverging route at that control point and at what speed the engineer is required to proceed over the switch. The names are Diverging Clear, Diverging Approach Medium, and Diverging Approach.

 

Another example: the aspect for Clear can be G/R or even G/R/R (we don't see too many three-headed signals in the Northwest Division any more, but there are still some around). Even though a red is displayed as part of the aspect, the indication is still Proceed.

[Glorious NSE]

Favourite quote from Al Krug's site - if it's not all red, it's not red at all...

http://krugtales.50megs.com/rrpictale/rrpictale.htm

[dave1905]

Here's how I see it. There are working railroaders who seem to think those who haven't passed a rules exam are unworthy. I know several. They'd probably flunk any rules exam not given by their favorite examiner. There are other working railroaders who say to those guys, "Geez, don't you get enough of that at work?" There are modelers and railfans who don't have to pass a rules exam who say, "Wow, if you take this really, really seriously, especially if you don't have to bluff your way past a single rules examiner, this is a really, really complex subject, and I'm happy with sorta-kinda, since my next project is wondering whether I can get a 1944 AAR boxcar for the xyz railroad superdetailed with just Joe Blow's kit, or if I have to kitbash it using a Balderdash as well." Each to his or her own!

There are also those working railroaders who have passed their rules exams every year for decades who take the time to try and explain real railroad operations to those who don't know about it. Nobody is "unworthy". Many people look for the exceptions and overlook the common items. Many time people get so hung up on minor visual differences, they overlook the purpose and operation may be the same.

 

Anybody can make things any way they want. Nobody is saying what anybody has to do. Just saying what the protoype does. How the modeler uses (or ignores) that information is his own business.