A simple question-what is an aspect? I keep hearing it but never explained. I knew the basics as a kid, especially with semaphores and enjoyed watching the arm move up or down
"Aspect" is the visible signal indication -- literally, the 'thing you see'.
You then determine the signal meaning from what you see.
On a tall signal:
Aspect = green over red.
Name = clear
Indication = Proceed not exceeding Normal Speed
(At least under Norac)
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
Aspect - the physical appearance of the signal (e.g. red light over green light)
Indication - the meaning of the aspect (e.g. "Slow Clear": proceed not exceeding slow speed past signal/turnouts)
An appropriate rule book will tell you the name/indication that corresponds to signal aspects.
An aspect can only have one indication; multiple different aspects can have the same Indication. e.g. Green or Green over Red or Green over Red over Red all mean "Clear".
Chris van der Heide
My Algoma Central Railway Modeling Blog
Brian Solomon authored two books about signaling:
RAILROAD SIGNALING, published in 2003 by MBI Publishing (currently available at Amazon for about $12);
CLASSIC RAILROAD SIGNALS: SEMAPHORES, SEARCHLIGHTS AND TOWERS, published 2015 by Voyageur (currently available at Amazon for about $29).
Both are aimed at non-technical readers/railfans. I think the former will come closer to answering many of your questions, although it may not have everything and it's been so long since I've read that I can't be certain how well it responds to your desire for "real-life scenarios, not just how it works". (Both books are also available through the Railway Educational Bureau of Simmons-Boardman Books, but at higher prices.)
Two related books - also available through Simmons-Boardman, neither of which I have read - are RULES & REGULATIONS GOVERNING RAILROAD SIGNAL AND TRAIN CONTROL SYSTEMS, which builds upon and explains the federal regulatory requirements for signaling; and TECHNICAL MANUAL FOR SIGNAL AND TRAIN CONTROL RULES which, from its title, I infer probably assumes a technical background.
Bill Hoerger
Oakland
Thanks, WGH.
I am currently reading Solomon's Railroad Signaling. I generally like the book. There is a lot of interesting info, and the photos are very good.
But one thing I really don't like is that in the first half of the book (I'm almost at the halfway point), he uses dozens of technical terms without having explained what those terms mean. Many are terms (or relate to concepts) I am not familiar with. So that is frustrating.
I think that some of the terms will get explained in the second part of the book; but a reader like me needs the explanations right there in the context of what is being written about, on the page where the concept is first encountered. (Or for the book to be structured differently.) The book begins with a lengthy history of signaling up to the present; then, later, I see that it will go into detail about all the various evolutions, where I hope some of the terms used in the first part will be better explained.
Terms like clear block (as opposed to just "clear," also mentioned), approach medium, medium clear, approach, caution, slow clear, slow approach, permissive block, restricting, etc., are used, but that doesn't mean much if the reader is not familiar with the definitions thereof. I can kinda guess at some of the meanings, but that's not good enough.
I'll let you know how much clarity is provided in the second half.
I am enjoying the book, for sure, but scratching my head a lot.
Lithonia OperatorBut one thing I really don't like is that in the first half of the book (I'm almost at the halfway point), he uses dozens of technical terms without having explained what those terms mean. Many are terms (or relate to concepts) I am not familiar with. So that is frustrating.
Sometimes authors don't follow scientific or scholarly conventions (where unfamiliar terms or acronyms/initialisms are defined or footnoted at the point they first appear) and rely instead on the glossary system. There, if you come across any term that is unfamiliar, you look it up in an indexed glossary, probably part of the 'end matter', and a good glossary will further footnote its entries to refer to explanatory material about the systems that employ the terms if those are not yet understood either.
This approach is well-suited to a complex text intended to be read by readers with a range of technical interest and experience, with at least a tacit understanding that 'novices' will gain sufficient knowledge in a first, perhaps quite halting reading but then breeze through the text on any subsequent pass.
Many of these terms are actually defined in NORAC, GCOR, and CROR and you may find it gainful to have these references open, either in PDF onscreen or as pages of selective printout, when reading a technical reference on signals, if for some reason there isn't an adequate glossary or equivalent provided for you.
I certainly concur that it is irritating not to have the necessary reference material at hand when reading, especially when the term(s) involved are not properly referenced in the index either. Books written before the turn of the 20th Century were often nearly obscene in this regard; you had to read them sequentially to get most of the information out of them, and you often had no idea whether they were relevant or even interesting to your research until you did.
But in the immediate case of Solomon's book, look for a glossary (I have not seen it, so I don't know what it has in that regard), bookmark it, use it religiously if you have even a hint of a question as to what something means, and be prepared to do an Internet search if the answer is somehow of low comprehensibility to you or more than normally difficult to find.
That's excellent advice, OM. Thanks for your response. I will have a look at the NORAC, GCOR and CROR material (which, as I'm sure no one will find surprising, is also unfamiliar to me.)
I meant to mention, though, that although this book does in fact have a glossary, it is a brief and very inadequate one.
Lithonia OperatorI meant to mention, though, that although this book does in fact have a glossary, it is a brief and very inadequate one.
As a suggestion:
I am an inveterate corner-folder and margin-commenter for books I own. What I suggest you do in cases like this is to add your own index and glossary entries as you come across them. If there is inadequate room make a note as to where blank pages are at the appropriate glossary or index entry point, and put the extended reference and further links to works or content there. Even if you don't use them, the next person who needs to read the book will thank you (if they have any sense).
Excellent idea. Thanks!
I never write on book pages, though. I am way too OC for that. But I'll use a large file card, stuck between pages.
I can't get this link 'hot', but it has signal charts for various railroads. Some are old and some are fairly recent. There is a link on the site, "common reference guide to signals" that is a pretty good way to learn how to interpret the signal aspects as they appear in the chart.
signals.jovet.net/rules/index.html
Jeff
Thanks, Jeff! That link is a gold mine! Much obliged.
There is a Glossary in Solomans book.
I am getting a lot out of this Solomon book. I like it. But here's something I totally don't get:
He has a sequence of photos, on a single track line, showing two masts with lower-quadrant semaphores, one on each side of the track, in ABS territory. Each mast has two semaphores. We are concerned with the mast on the right (the one on the other side does not face us. We are looking down the track as if we are a train approaching the signals. The caption lets us know that a train is coming toward us. As the train gets closer (we don't see it until later, in a pic where it's right at the signals), the aspects change. In the third frame, we see that both semaphores are horizontal, and Solomon says it means "stop and proceed;" and the fact that we see that aspect is because the opposing train has entered the block.
He explains "our train" must stop, then can proceed at 15 mph.
Now, why the heck would we enter a block we know a train is in, particularly an opposing train?!?!
That train has already seen the last signal he will encounter before he gets to us. Well, actually, he will see the signal on the left, which we see the back of, but only when he sees us also. And we have stopped and now entered the block. Yikes.
This seems like a perfect recipe for disaster! What am I missing? Is Solomon perhaps confused himself.
Not only would I not want to enter that block, I would want to start backing up like hell to minimize the impact!
The more I explore this, the more I realize there are myriad ways signaling is done, so my questions, like the one above, often demand answers too involved for a web forum.
But here's a more bite-sized one. I see that one of the various ways to indicate clear is just one green light; but a green over two reds means the same thing. Which begs the question, why not use just the lone green?
What are the two reds telling us, that somehow complements the green on top?
Lithonia OperatorI am getting a lot out of this Solomon book. I like it. But here's something I totally don't get: He has a sequence of photos, on a single track line, showing two masts with lower-quadrant semaphores, one on each side of the track, in ABS territory. Each mast has two semaphores. We are concerned with the mast on the right (the one on the other side does not face us. We are looking down the track as if we are a train approaching the signals. The caption lets us know that a train is coming toward us. As the train gets closer (we don't see it until later, in a pic where it's right at the signals), the aspects change. In the third frame, we see that both semaphores are horizontal, and Solomon says it means "stop and proceed;" and the fact that we see that aspect is because the opposing train has entered the block. He explains "our train" must stop, then can proceed at 15 mph. Now, why the heck would we enter a block we know a train is in, particularly an opposing train?!?! That train has already seen the last signal he will encounter before he gets to us. Well, actually, he will see the signal on the left, which we see the back of, but only when he sees us also. And we have stopped and now entered the block. Yikes. This seems like a perfect recipe for disaster! What am I missing? Is Solomon perhaps confused himself. Not only would I not want to enter that block, I would want to start backing up like hell to minimize the impact!
Don't know the signal system you are referring to - that being said. The obligation of both trains accepting such signals is to move at Restricted Speed, and in addition to the 15 MPH maximum what is another requirement of Restricted Speed? A speed which will permit STOPPING WITHIN ONE HALF THE RANGE OF VISION - the scenario you presented is the reason for the one half the range of vision stipulation. If the trains touch each other, that becomes prima facia evidence that at least one of the trains wasn't fully following the obligations of Restricted Speed.
Never too old to have a happy childhood!
Lithonia OperatorThe more I explore this, the more I realize there are myriad ways signaling is done, so my questions, like the one above, often demand answers too involved for a web forum. But here's a more bite-sized one. I see that one of the various ways to indicate clear is just one green light; but a green over two reds means the same thing. Which begs the question, why not use just the lone green? What are the two reds telling us, that somehow complements the green on top?
The multiple head signals are able to display more indications. The configuration of signal at any particular location are dictated by all the situations those signals must cover.
As you read through ALL the signal indications, you will notice that there are numerous indications where there are different colors displayed on each of the signal heads. A 'dark' signal head, where there are multiples, is considered as a improperly displayed signal and the crew must operate in accordance with the understanding that that signal is displaying it's Most Restrictive indication.
For a signal with Number Plate - the most restrictive is Restricted Proceed. For a signal Without a Number Plate - the most restrictive is STOP.
Well, I did wonder if the two reds were basically saying "we are operating; we are not defective." But why wouldn't they have greens lit, which would also convey that?
Remember - signal lights were something that 'back in the days got added to existing semaphore signal installations. Why the semaphores were designed as multiple arms on a common mast goes back to the very elements of 'mechanical interlocking' systems where the various 'notched steel bars' permitted or prevented the lining of the signals and their various aspects.
Modern signal systems have removed the semaphore arms and left us with the corresponding colored lights to display the signal aspects.
Having been raised on the B&O Color Position Light signals - I much prefer them as being the most easily understood of all signal systems.
BaltACDHaving been raised on the B&O Color Position Light signals - I much prefer them as being the most easily understood of all signal systems.
Right up until you start using them for route indication. Then I think you get lost in lunar-white-light afterthoughts.
For speed and block indications, there is possibly none better. As someone once remarked of Patenall's system 'anytime I see a green anywhere I go like hell'. (And of course CPLs are so cool...)
Overmod BaltACD Having been raised on the B&O Color Position Light signals - I much prefer them as being the most easily understood of all signal systems. Right up until you start using them for route indication. Then I think you get lost in lunar-white-light afterthoughts. For speed and block indications, there is possibly none better. As someone once remarked of Patenall's system 'anytime I see a green anywhere I go like hell'. (And of course CPLs are so cool...)
BaltACD Having been raised on the B&O Color Position Light signals - I much prefer them as being the most easily understood of all signal systems.
Lunar White = Restricted Speed
Guys, I really appreciate the input, and I'm really not trying to be a pain in the butt (honest), but ...
Why would you display a green over two reds, when you could display three greens in a vertical stack, if the meaning is "clear?" You CAN make all the heads show green, right? Or not?
Quoting Balt: "For a signal with Number Plate - the most restrictive is Restricted Proceed. For a signal Without a Number Plate - the most restrictive is STOP."
This may not apply in Canada; every signal that I saw when crossing Canada had a number plate. I asked about this a few years back, and, as I recall, a single head indicated that it was a lineside signal, and two or more heads indicatted that it was an interlocking signal.
Johnny
Lithonia Operator Guys, I really appreciate the input, and I'm really not trying to be a pain in the butt (honest), but ... Why would you display a green over two reds, when you could display three greens in a vertical stack, if the meaning is "clear?" You CAN make all the heads show green, right? Or not?
Not necessarily.
The signal for the southwest transfer, going onto the E-W mainline at Deshler has one over two over three colors. The top signal is always red, as there will never be a "high speed" movement there. The middle can show red or amber, indicating a medium approach or the like.
The bottom head can show all three colors.
The relative position of the green signal conveys further, specific, meaning. A bottom green may indicate a diverging movement, f'rinstance. Lighting it up as green would actually conflict with the other greens.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Lithonia OperatorGuys, I really appreciate the input, and I'm really not trying to be a pain in the butt (honest), but ... Why would you display a green over two reds, when you could display three greens in a vertical stack, if the meaning is "clear?" You CAN make all the heads show green, right? Or not?
Think back to the additional 'horsepower' that would have been required to move from their 'fail safe' gravity powered position of down for red and up for green and mid-way for yellow. When electric lights entered the system, they just supplemented or replaced what had previously existed. Search around the web for 'old time' rule books from the teens, twenties or thirties - and look at their signal indications.
Virtually every process on railroads is built upon what existed before the new process started to be implemented - no process - not even PTC - is being implemented as a 'new whole cloth'. PTC is being implemented as a overlay on the prior existing systems - be that signal indication or Track Warrants.
When I was working as a Train Order Operator, a number of the interlockings I worked were still 'pipeline' operated. By the time I was working, the signals were all electric and operated by relays connected to the pipeline operating levels. I have no fear in stating that when the plants were 'new' and semaphore signals were the standard, individual levers would operate individual elements of the semaphores - the more things a pipeline operates - the more 'power' the operator must apply to the operating lever. When it comes to lining crossover, with both switches on the same pipeline lever - you have to EXPLODE on the lever. I would imagine a semaphore would be similar in nature.
Remember, anything that is a 'radical' change, requires a heavy period of training among all the employees that will be affected in any way by the change. It is easier, and cheaper, to use the formats that already exist.
DeggestyQuoting Balt: "For a signal with Number Plate - the most restrictive is Restricted Proceed. For a signal Without a Number Plate - the most restrictive is STOP." This may not apply in Canada; every signal that I saw when crossing Canada had a number plate. I asked about this a few years back, and, as I recall, a single head indicated that it was a lineside signal, and two or more heads indicatted that it was an interlocking signal.
I have no experience in Canadian railroading. What I stated is the US standard, as far as I know.
Every railroad may have some locations that have non-standard signal displays. On my former territory - there was one non-number plate signal, it was not controlled by the Train Dispatcher. Its purpose was to hold trains off road crossings between it and the next control point when the control point's signal was not line for movement. When the Control Point signal was lined that signal would relay a proceed indication of one variety or another.
Thanks, tree. I didn't realize some heads can't show all colors. And that's a very good point about confusion with other greens in the vicinity; I had not thought about that before. If an engineer knows he's supposed to be seeing a green over two reds at that particular spot, then he's going to be lot more sure that that indeed is his signal.
I had never really thought about the diversity and sheer number of different situations, and the ways they can be dealt with. The subject is much more complicated than I ever imagined. It's easy to understand why detour trains need to use host-road pilots.
Lithonia OperatorYou CAN make all the heads show green, right? Or not?
There are many cases where heads are restricted to yellow/red or red aspects. These were mentioned many times in the Sunset Route two-tracking thread.
We have an example in the approach to what used to be called Forrest Yard on the ex-Southern in Memphis. There is never going to be an occasion to show 'green' on some of the approach signals -- they are at their most 'permissive' when showing the occasional yellow in some positions. When there are separate color lights per head, they will only be yellow and red; when searchlights, there would be no position corresponding to 'green' in the internal moving filter.
We have an example in the approach to what used to be called Forrest Yard on the ex-Southern in Memphis. There is never going to be an occasion to show 'green' on some of the approach signals -- they are at their most 'permissive' when showing the occasional yellow in some positions. When there are separate color lights per head, they will only be yellow and red.
A searchlight, in a comparable situation, would have no position corresponding to 'green' in the internal moving filter. Relay alignment that would show 'green' on a typical wayside would produce no more than yellow at such a signal.
Lithonia OperatorThanks, tree. I didn't realize some heads can't show all colors.
For an interesting study of such variations, look up the rapidly disappearing B&O Color Position Lights (CPL). A full CPL had the main disk with red, amber, green, and lunar lamps, as well as three top markers, and three bottom markers. The various combinations conveyed a wide variety of aspects.
But if you look at specific locations, you'll find CPLs with no lunar and only one or two markers on top or bottom. That's because the conditions that would require the missing lamps don't exist at that specific location.
You'll find similar situations with PRR position lights, and I think N&W had CPLs as well.
When searchlights were the thing, you'd simply have one to three heads that displayed the appropriate colors.
Type G signals would have unused colors blanked out.
Today's "Darth Vader" signals simply have only the color lamps needed, as with the Deshler 1-2-3 I mentioned.
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