Rail road signals and their placement

[torikoos]

Hi all, hope you've all survived Christmas and had a lot of fun while doing so!

I have a question in regards to signal placement . While I have some understanding on the aspects a signal can show, I'm not too sure about it's placement.
Specifically, I'm thinking of a modern light signal mast, that has two signal heads, each having red yellow and green lights. Let's say it's situated next to a double track main line, on which side would it most commonly be ? I asume this would be the right side, but I've also seen signals on the other side of the tracks. Which of the signal heads would be for the right hand track , the top or the bottom? And what if it's placed on the left hand side of the tracks?
(BLMA models both makes left and right handed signals).

Cheers !
Koos

PS: All the best wishes in advance for 2012!

[Puddlejumper]

Koos,
Typically when you have a double main, if the signals for each track are on their own masts then they would appear on the trackside of the track they govern. In other words, the signal to the left of the tracks would govern the left track, the signal to the right of the tracks would govern the right track.



When both signal share a common mast on one side or the other of the tracks, the left signal would govern the left, the right governs the right. In this case the mast must be tall enough to be seen by trains on the opposite track from the signal, even when a train may be on the track between the signal and the governed track.



In the rare case when only one track of a double main has a signal, but it is on the opposite side of the tracks, there will be a "dummy" mast on the non signalled side, like this one. In this case the signal governs the left track.



There are also overhead signal cantilevers, the signals are located roughly over the track they govern or, as above, left governs left, right governs right. There are of course many, MANY, exceptions, cases where signals may be located in unusual locations due to obscured visibility, tight quarters, or any number of other reasons. In these cases, the information would be provided in the Timetable Special Instructions governing the division that is being operated on, and required to be studied an familiar to all crews operating over that territory.

I am sure I missed something, I haven't been employed by a railroad in T&E service now in over 10 years. There are others who will amend or add to what I have said. Sorry about the poor artwork, i'm no artist.

Dave

[Puddlejumper]

Which of the signal heads would be for the right hand track , the top or the bottom?

Sorry I missed this part. All signal heads, or lights, on a single mast (pole) govern the same track. Each track has it's own signal head or heads on it's own mast. In the examples above, even though the left signal has 2 sets of lights, top and bottom, this is ONE signal ASPECT that INDICATES what a train is allowed to do. If the top has a green light, and the bottom a red light, the ASPECT is CLEAR, the INDICATION is PROCEED.

If the top was yellow and the bottom red, the ASPECT is APPROACH, the INDICATION is PROCEED PREPARED TO STOP SHORT OF NEXT SIGNAL.

If the top was red and the bottom green, the ASPECT would be MEDIUM CLEAR, the INDICATION would be PROCEED, NOT EXCEEDING MEDIUM SPEED THOUGH INTERLOCKINGS AND SWITCHES AND THEN PROCEED AT MAXIMUM PERMITTED SPEED.

The ASPECT is what the signal shows you, the INDICATION is what the aspect tells you how the train is to proceed (or not proceed as the case may be)

Typically, on the eastern railroads I worked on, intermediate (or permissive) signals were located between interlockings where there are no switches or diverging routes (not including industries) and had only 1 head. Signals 1 block away from an interlocking had 2 heads, and interlocking or absolute signals had 3 heads. An example of a 3 head signal would be red over yellow over green. The ASPECT is MEDIUM APPROACH SLOW, the INDICATION is PROCEED NOT EXCEEDING MEDIUM SPEED THROUGH SWITCHES AND INTERLOCKINGS AND THEN PROCEED APPROACHING NEXT SIGNAL NOT EXCEEDING SLOW SPEED.

It gets pretty complicated after awhile. I know I was long winded, sorry about that. These are, of course, railroad specific and are the rules I knew 10 years ago. They may be different on western railroads.

[BR60103]

I always understood that if the lights were hung on the same side of the mast (usually right) it was an interlocking signal and if the lights were on opposite sides (left on top) it was a block signal. Interlocking signals also performed block signal functions (to keep following trains apart). Interlocking signals (Canadian rule book, 1962) usually described speeds (restricted, slow, medium or limited) that were to be observed through the interlocking and then the speed to be used to the next signal.
And some RRs used signals to tell the crew which route they would follow through the interlocking.

[railohio]

Specifically, I'm thinking of a modern light signal mast, that has two signal heads, each having red yellow and green lights. Let's say it's situated next to a double track main line, on which side would it most commonly be ? I asume this would be the right side, but I've also seen signals on the other side of the tracks. Which of the signal heads would be for the right hand track , the top or the bottom? And what if it's placed on the left hand side of the tracks?

Speaking very generally...

Signals with two heads stacked vertically are used at interlockings while signals with a single head are used as intermediate block signals. (Some intermediates have two heads when they are adjacent to interlocking signals.) Signals with two heads horizontally on a bracket are used by some railroads in double track territory instead of having signals on both sides of the tracks.

Signal placement will largely depend on the era and signaling system. By American standards signals are placed on the outside of double track territory. With full Centralized Traffic Control (CTC) trains can operate on any track in both directions without restrictions. As such signals appear in both directions for all tracks on the outside of the right-of-way.

For basic block signal operation (Rule 251) signals appear only for the designated direction on each track on the outside of the right-of-way. Trains operating against the current of traffic will require specific permission from the train dispatcher to do so.


Examples:

Single-head intermediate block signal facing the camera; double-head intermediate block signal facing train

Modern signals mounted horizontally on bracket for double track territory

Classic signals mounted horizontally on bracket for double track territory

Classic signals mounted on the outside of the right-of-way for double track territory


Further reading:

Railroad signals

Glossary of railroad signal terms

Railroad's traffic control systems

[dave1905]

Signals with two heads stacked vertically are used at interlockings while signals with a single head are used as intermediate block signals. {/quote]

Not necessarily. A two headed signal in the western half of the US typically indicates a diverging aspect, which can be a control point or an interlocking. You can also have an automatic interlocking with single head signals.

Signal placement will largely depend on the era and signaling system. By American standards signals are placed on the outside of double track territory. With full Centralized Traffic Control (CTC) trains can operate on any track in both directions without restrictions. As such signals appear in both directions for all tracks on the outside of the right-of-way.

For basic block signal operation (Rule 251) signals appear only for the designated direction on each track on the outside of the right-of-way. Trains operating against the current of traffic will require specific permission from the train dispatcher to do so.

Mixing systems.

CTC and ABS (a "basic" block signal system) is signaled in both directions. Rule 251 is current of traffic which is signaled in one direction (the other direction is considered non-signalled territory).

[torikoos]

Thank you all for your explanations.
It looks like there is a lot of variety, and I'm not sure I fully understand all of it yet, is there a publication (that is still available) that would explain all of this too, sort of a 'guide to american railroad signals for dummies' , or text books you get on the subject published by the railroads? I'm sure you go through some sort of training when you are going to be an engineer? :-)

Cheers,

Koos

[railohio]

Railroad Signaling by Brian Solomon is probably the best overall explanation of how it works.

Tony Koester's Realistic Model Railroad Operation has a chapter on different forms of signaling and how they can be applied to a model railroading.

[railohio]

Railroads have various training methods for crews. If you are interested in a specific railroad you should collect rule books and employee timetables from that operation as signal rules will vary a bit by railroad. Most training material will focus on aspects and indications. Information on signal placement will be limited to how crews can identify which signals govern their movements.

CSX publishes a book of signal indications but eBay generally removes any auction for CSX company materials. NORAC, a unified rules system for Northeast railroads, has very handy laminated sheets with signal indications but I don't see any on eBay at the moment. The best place to acquire items like this is at railroad paper trade shows, but being across the Pond I wouldn't being to guess at their pricing or availability to you.

[faraway]

The are several GCOR as PDF files available. My last used link is broken but this one looks alive http://www.utu1904.com/files/Download/GCOR_6th_ed.pdf

[jwb]

The best single source I've seen on signals and operation is Bruce Chubb's How to Operate Your Model Railroad. This is long out of print, and the people on the cover are very 1970s, but it's available used at a reasonable price <!-- m --><a class="postlink" href="http://www.amazon.com/gp/offer-listing/0890245282/ref=sr_1_1_olp?ie=UTF8&qid=1325172821&sr=8-1&condition=used">http://www.amazon.com/gp/offer-listing/ ... ition=used</a><!-- m -->

The whole question of model railroad operation is bound up in another thread here, whether the hobby is a solo or group activity. If you operate mostly alone, your approach is going to be very different from the way it would be if you have a regular group. I operate a lone, and my challenge is to have a signal system that mimics CTC without the need for a dispatcher. On the other hand, I have lots of challenges, and I have to do the best I can with the resources I have available.

I also remember an MR article from about 1960, where the guy made detailed models of the unique C&NW semaphores. He was interested in the models themselves, and they were otherwise unlit and not operational. He got around that by modeling a maintainer on site and saying they were out of service for that reason. Naturally there are rules that cover this situation on the prototype.

[BR60103]

My thread on Canadian Signal indications. (1962)
<!-- l --><a class="postlink-local" href="http://www.the-gauge.net/forum/viewtopic.php?f=27&t=2410&p=38973&hilit=+signals#p38973">viewtopic.php?f=27&t=2410&p=38973&hilit=+signals#p38973</a><!-- l -->
The pages were copied from an old rulebook and have some amendments made by the original owner.