I have always been confused about some aspects of signaling, and how trains are required to proceed (or not) under certain signal conditions.
Can anyone recommend a good book on this subject? I have read the chapter in The Railroad: What it is ... , but some of that confused me.
I'd like something aimed at railfans without any technical background, and is thorough, explaining various real-life scenarios, not just how it works (or is supposed to work).
Besides mass-market books, is it possible to find railroad training manuals from the days before simulators, etc., from which potential engineers had to learn this subject only from reading, and seeing diagrams in the book?
As an operator I always knew the answer to the question, "Is anything coming?" But as a railfan, I basically never know. How much can one discern just from seeing a block signal? Not much? And it varies spending on the system, right?
If I happen to know that it's approach-lit, does that mean any indication means something is relatively near? If so, what can I learn as to train direction? If a signal is dark (and I know the line is active), and it's single-track, does this always mean that nothing is coming from either direction?
Will an entire railroad use the same type of system? I am thinking not, because of acquisitions and mergers.
Does presence of PTC skew what a railfan can discern from seeing a signal?
Etc., etc.
HELP!!
Still in training.
Start with a couple of the online guides to railroad/railway signaling.
Systems of signaling can vary, in their details, widely between railroads and types of line. Some of the railroaders here can give you current information on their particular practices.
Keep in mind that early block signals were not intended as 'traffic signals' but only to show where other trains were, or were likely to be. There were two philosophies regarding how to display 'stop' signals (which were not, initially, always 'red') -- one way is to have all signals kept showing 'stop' until an 'approved' route has been set -- this is how Patenall set up the B&O CPLs, so an engineer once said 'if I see a green anywhere I know I can go like hell'. The other way is to have signals show green any time a line is open, and red only for known or detected restriction ... this simplifies the relay design and parts count.
Lithonia OperatorI have always been confused about some aspects of signaling, and how trains are required to proceed (or not) under certain signal conditions. Can anyone recommend a good book on this subject?
The good book you are looking for is the rulebook for the time and railroad you are interested in. You should be able to pick up what you want off ebay, but may take some time and patience.
The GN/NP Archives, which are online under that name, has at least one Gonsolidated Code of Operating Rules that you can read and download. IIRC it is under the Cascade Division heading.
Mac McCulloch
I spend a fair amount of time on the Deshler rail cam. There are still several color position lights in service there. I've got a fair idea of what they show, but still check a reference chart. The chart shows the aspect and the applicable rule, which you could look up in the rules PNWRMN mentioned.
Bearing in mind that Deshler is a big interlocking. If you see an aspect there other than stop, it means there will be traffic.
Understanding some basic terms (like "medium speed" or "restricted") helps a lot once you understand the basics.
For "stacked" signals - two or three on one mast, a rule of thumb is that the top head is for high speed, the middle head is medium speed, and the bottom head is for slow speed.
That's why you'll see such signals with a top head with just one color - red. There will never be a high speed movement through that signal. Bearing in mind that "high speed" will just be maximum track speed, not necessarily super fast.
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...
It may be dated (1955) but John Armstrong's "All About Signals" would be a good starting point for the theory and practice of both block signals and interlockings. It might take some digging for background on Direct Train Control and Track Warrent Control.
Lithonia Operator.... As an operator I always knew the answer to the question, "Is anything coming?" But as a railfan, I basically never know. How much can one discern just from seeing a block signal? Not much? And it varies spending on the system, right? If I happen to know that it's approach-lit, does that mean any indication means something is relatively near? If so, what can I learn as to train direction? If a signal is dark (and I know the line is active), and it's single-track, does this always mean that nothing is coming from either direction? Will an entire railroad use the same type of system? I am thinking not, because of acquisitions and mergers. Does presence of PTC skew what a railfan can discern from seeing a signal? Etc., etc. HELP!!
One thing to remember about signal systems on todays Class 1 carriers. Most of the signal systems were installed by the Fallen Flag carriers over time as both funds became available and increased traffic requirements warranted their installation. Each initial installation would be done with 'state of the art' equipment that was available at the time. What was state of the art in the 1920's was not state of the art in the 1940's and so on; that being said all the installations had to work in concert with each other. Each new installation would bring its own state of the art into the equation; additionally every head of a carriers signal department would have their own 'pet theories' of operation and implementation of the hardware on the individual carriers they headed. As the heads of the signal department changed over time, so did the pet theories. Those pet theories would extend to purchasing signal equipment from one vendor as opposed to other vendors in the marketplace.
In the case of CSX - You had signal designed for the ACL A&WP, B&O, C&O, L&N, Georgia, SAL that were then modified/enhanced by SCL and Chessie System and then brought together under CSX - a lot of change over the years.
PTC has had the effect of renewing the signal systems on the most mileage of Class 1 carriers that has EVER happened within one period of time; as most of the signal equipment changes in the field have happened nominally within the past 5 years.
Whether signals are approach lit or constantly lit are a choice each carrier make and it may be required because of the signal equipment installed.
In approch lit territory - if you see a signal lit, that means a train is in the signal block approaching the signal, it does not indicate the direction of the train - you could have just missed a train moving away from the signal, but it still occupies the signal block.
If signals indicate some kind of indication better than Restricted Proceed that will tend to indicate that a train will be approaching to accept that signal indication and continue moving in the direction that the signal authorizes. With the above being stated, Dispatchers in CTC territory will frequently line signals in the reverse direction for trains after they meet - in fact with CADS lining multiple moves to take place in sequence is one of the functions of the CADS software that allows lining switches and signals for future moves at the Dispatcher's discretion.
Never too old to have a happy childhood!
Back when the N&W's Powhatan Arrow had a dome coach, I rode it from Cincinnati to Norfolk, taking advantage of the dome most of the way. We left Cincinnati on the B&O, and then made use of the PRR before we reached N&W rails. Noticing the signals, I asked the flagman about the significance of the lunar whites. I do not remember his exact answer, but on one railroad, it had one significance--and on the other road it had the opposite significance. The engine crew really had o know the territory.
Johnny
A major point about Signalling that hasn't been mentioned yet is that Eastern railroads use "Speed Signalling", while the Western railroads use "Route Signalling".
CSSHEGEWISCH It may be dated (1955) but John Armstrong's "All About Signals" would be a good starting point for the theory and practice of both block signals and interlockings. It might take some digging for background on Direct Train Control and Track Warrent Control.
I agree. Start with "All About Signals". John Armstrong was a great "explainer".
What's changed since then is some of the hardware - there are microprocessor based interlockings, for example - but the basics remain the same, including understanding signal aspects and indications.
PTC, generally, is an enforcement overlay on the exiting signal systems, so you can add that in once you have the basics down.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
The most important thing is, "you gotta know the territory."That caused a serious Amtrak accident a few years ago when a western-trained engineer was at the controls of the Pere Marquette coming into Chicago. He encountered a red-over-yellow signal in the vicinity of Englewood, and read it as "Diverging Approach". On the NS, though, it was "Restricting." He may have been ready to stop at the next signal, but he wasn't ready to stop short (withn half the range of vision) of the train that was within that block. Fortunately, his engine rode over the top of the cars in the stopped freight. The fault was his: one has to be familiar with the signals and other operating practices of the territory he's assigned to.Generally speaking, it can get complicated. We cross the tracks at the one grade crossing in town where one can see signals in both directions. To this day my wife doesn't understand why a green signal looking west is "meh" to me, but in the other direction it means I'm going to want to stay close to the tracks.
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
Thanks folks, for all of the book suggestions, and the comments regarding signaling.
Is anyone familiar with the book Introduction to North American Railway Signaling? It would be pricey to get one; but if it was super good, I might consider it.
Check out TransAlert. It's owned by Simmons-Boardman.
Their main page, for railroad items.
https://www.transalert.com/bookstore/Rail/
Their page for railroad communications and signalling.
https://www.transalert.com/bookstore/Rail/Signal___Communications/
Jeff
PTC, the system that we use, turns on signals that are normally approach lit when the train enters the preceeding block for 6 miles in advance of the train. It has something to do with PTC "seeing and reading" the signals.
Since that system is used by most of the freight railroads, I imagine it works the same way for the other railroads, too.
CShaveRR Generally speaking, it can get complicated. We cross the tracks at the one grade crossing in town where one can see signals in both directions. To this day my wife doesn't understand why a green signal looking west is "meh" to me, but in the other direction it means I'm going to want to stay close to the tracks.
Generally speaking, it can get complicated. We cross the tracks at the one grade crossing in town where one can see signals in both directions. To this day my wife doesn't understand why a green signal looking west is "meh" to me, but in the other direction it means I'm going to want to stay close to the tracks.
OK, I'll bite- I don't understand either, but I bet you can explain it to me. Green to the west doesn't mean a westbound is coming?
I do like the PTC-modified approach-lit signals- gives you a bit more warning that something is coming.
Brian (IA) http://blhanel.rrpicturearchives.net.
oltmannd CSSHEGEWISCH It may be dated (1955) but John Armstrong's "All About Signals" would be a good starting point for the theory and practice of both block signals and interlockings. It might take some digging for background on Direct Train Control and Track Warrent Control. I agree. Start with "All About Signals". John Armstrong was a great "explainer". What's changed since then is some of the hardware - there are microprocessor based interlockings, for example - but the basics remain the same, including understanding signal aspects and indications. PTC, generally, is an enforcement overlay on the exiting signal systems, so you can add that in once you have the basics down.
Why doesn't Kalmbach reprint John Armstrong's excellent books? Is there no market for them? Yes, it is out-of-date in that it is set in the steam-diesel transition era, but "Track Planning for Reliable Operation" offers information for both the railfan observing 12 inches-to-the-foot railroads along with the railroad modeler that is simply not available in Kalmbach's current offerings.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
blhanel CShaveRR Generally speaking, it can get complicated. We cross the tracks at the one grade crossing in town where one can see signals in both directions. To this day my wife doesn't understand why a green signal looking west is "meh" to me, but in the other direction it means I'm going to want to stay close to the tracks. OK, I'll bite- I don't understand either, but I bet you can explain it to me. Green to the west doesn't mean a westbound is coming? I do like the PTC-modified approach-lit signals- gives you a bit more warning that something is coming.
OK, I'm still a little confused there- I've always thought that a non-red aspect in ANY direction means the dispatcher has lined that track up for a train headed that way. A non-red looking west means a westbound is either imminent or eventually will arrive, and vice-versa for the other direction. It seems from my observations that non-approach-lit signals (such as the Beverly/Bertram/Mechanicsville crossovers) will stay red until the dispatcher sets them up for impending traffic. But then we're alot simpler out here...
blhanel OK, I'm still a little confused there- I've always thought that a non-red aspect in ANY direction means the dispatcher has lined that track up for a train headed that way. A non-red looking west means a westbound is either imminent or eventually will arrive, and vice-versa for the other direction. It seems from my observations that non-approach-lit signals (such as the Beverly/Bertram/Mechanicsville crossovers) will stay red until the dispatcher sets them up for impending traffic. But then we're alot simpler out here...
The problem is that Brian only sees the signals when they're lit up (approach lit) by either a train in the block or by the PTC for a closely approaching train.
The intermediate signals between the control points are plain automatic block signals. If you get far enough away from the control points so you don't get advance approach and approach indications for a cp not lined up, where you have three unoccupied signal blocks ahead of an intermediate signal with nothing lined up in the opposing direction, the signals if they were lit up would be green.
When the dispatcher lines up an opposing move, for example an eastbound on track 2 at Beverly, the signal circuitry shunts the block signals for opposing (westward in this case) to the next control point at Bertram. All the westward intermediates on #2 would "tumble down" to red. (Before UP went to approach lit in this area, you used to be able to see this happen in locations where you could see 2 or 3 block signals. You could watch in succession as each signal went from green to red.) The westward intermediates at the Otis detector and I think Otis Rd would normally show green if they were lit up with nothing lined through in either direction.
Hopefully the mud is a bit clearer.
jeffhergert blhanel OK, I'm still a little confused there- I've always thought that a non-red aspect in ANY direction means the dispatcher has lined that track up for a train headed that way. A non-red looking west means a westbound is either imminent or eventually will arrive, and vice-versa for the other direction. It seems from my observations that non-approach-lit signals (such as the Beverly/Bertram/Mechanicsville crossovers) will stay red until the dispatcher sets them up for impending traffic. But then we're alot simpler out here... The problem is that Brian only sees the signals when they're lit up (approach lit) by either a train in the block or by the PTC for a closely approaching train. The intermediate signals between the control points are plain automatic block signals. If you get far enough away from the control points so you don't get advance approach and approach indications for a cp not lined up, where you have three unoccupied signal blocks ahead of an intermediate signal with nothing lined up in the opposing direction, the signals if they were lit up would be green. When the dispatcher lines up an opposing move, for example an eastbound on track 2 at Beverly, the signal circuitry shunts the block signals for opposing (westward in this case) to the next control point at Bertram. All the westward intermediates on #2 would "tumble down" to red. (Before UP went to approach lit in this area, you used to be able to see this happen in locations where you could see 2 or 3 block signals. You could watch in succession as each signal went from green to red.) The westward intermediates at the Otis detector and I think Otis Rd would normally show green if they were lit up with nothing lined through in either direction. Hopefully the mud is a bit clearer. Jeff
What is a control point?
Doesn't a circuit at every signal "know" when a train goes by? And does it know in which direction it goes by?
(No mystery why I'm looking for a book, right?)
Lithonia OperatorWhat is a control point? Doesn't a circuit at every signal "know" when a train goes by? And does it know in which direction it goes by? (No mystery why I'm looking for a book, right?)
A control point is a location where the Train Dispatcher (or Control Operator) has control of the switches, derails and Absolute Signals that protect the various routes that can be arranged at the Control Point.
Second question's answer. The signal itself does not detect a train. Classic signalling had track-circuits detect trains. Say signals are spaced every mile along a particular track. In the vacinity of each signal there is an insulated rail joint. A voltage is applied between the two rails continously. Without a train present the current is very small becauses the resistance of the circuit thorugh the wood ties is high, even when wet. But the presence of a train provides a steel current path between the two rails, and the current then increases by an order of magnitute or more, at least multiplied by ten. Through relays or solid-state switching, this sets the signals protecting the block between signals at red, stop, and usually the next signal will be yellow.
In classic automatic block siginal terriroty, the signals at any one moment do not know which way the train is movoing, only that the block is occupied. However, more advanced and modern signalling involves analyss and a dispatcher watching progress on a model board linked to the signal system may be provided with this information on a continuous basis, although on older CTC systems he knows which way the train is moving just by having obsserved the progress of the lights on the model board showing occupancy.
daveklepperClassic signalling had track-circuits detect trains.
Those circuits were often coded, which is how you can have a road crossing within a block and have both operate correctly. It all had (and may still) to do with the rates of pulses.
Before solid state became a thing, those pulses were a function of relays, which might cycle millions of times in their lifetime.
Looking at a place like the diamond at Deshler, OH gives me a great deal of respect for the signal folks who designed and now maintain systems that know which crossing to activate while having the signals display the correct aspects, based partly on what the DS wants, and partly on track occupancy.
This is also how cab signalling works - a sensor picks up that pulse rate from the upcoming signal and displays the appropriate aspect in the cab.
I'm not smart enough on such systems to say much of anything more - that's best left to a good book on the topic.
Since the Southwest Service line is reverse signaled, I use the signals just west of the Oak Lawn station as an early tipoff to train time and occasionally which track it will use. The signal on the usual outbound track is usually at yellow-over-red since it also serves as a distant signal for Chicago Ridge Junction. When the usual inbound track signal displays red-over-red, it indicates that the track has been set up for an inbound train.
jeffhergert Check out TransAlert. It's owned by Simmons-Boardman. Their main page, for railroad items. https://www.transalert.com/bookstore/Rail/ Their page for railroad communications and signalling. https://www.transalert.com/bookstore/Rail/Signal___Communications/ Jeff
Thanks for the links, unfortunately, I had to spend money there.........
My sister is going to kill me when she tries lifting that package..........
Randy Vos
"Ever have one of those days where you couldn't hit the ground with your hat??" - Waylon Jennings
"May the Lord take a liking to you and blow you up, real good" - SCTV
Treex68: A more modern approach, avoiding the use of rapidly repeating relays, was simply to use alternating current at different frequencies, driven by amplifiers with oscilators at different frequencies. This was system-wide PRR practice. Obviously, 60 Hz and 25 and anything very close to these frequencies were avoided.
daveklepper Treex68: A more modern approach, avoiding the use of rapidly repeating relays, was simply to use alternating current at different frequencies, driven by amplifiers with oscilators at different frequencies. This was system-wide PRR practice. Obviously, 60 Hz and 25 and anything very close to these frequencies were avoided.
Indeed. I pointed out the relay thing as a testament to the durability of those relays.
I would be surprised, but not entirely, to find such relays still in use. Crossings, f'rinstance, often now use Doppler to figure out when to activate the crossing protection. That would be hard to do with relays....
tree68 daveklepper Treex68: A more modern approach, avoiding the use of rapidly repeating relays, was simply to use alternating current at different frequencies, driven by amplifiers with oscilators at different frequencies. This was system-wide PRR practice. Obviously, 60 Hz and 25 and anything very close to these frequencies were avoided. Indeed. I pointed out the relay thing as a testament to the durability of those relays. I would be surprised, but not entirely, to find such relays still in use. Crossings, f'rinstance, often now use Doppler to figure out when to activate the crossing protection. That would be hard to do with relays....
I believe that Control Points, that for the various reasons, have not been updated to PTC standards on the Class 1 carriers as well as other carriers that don't fall under PTC requirements are mostly using equipment in those control points that are relay operated.
On CSX when Control Points were being updated to PTC standards, the old signal bungalow would be removed and a new, prewired and equipped signal bungalow would be installed and tested for proper function, in most cases new signal displays were also being activated. These removals and installations happend under local Signal Suspensions for the particular Control Points involved.
Here's a link to Absolute Permissive Block signal system. It's an outgrowth of plain Automatic Block signalling. APB has the 'tumble down' feature for opposing signals that CTC has. The difference (in simple terms) is in APB, the train occupying a block causes the signal changes. In CTC the dispatcher/control operator lining up a route causes the signal changes even if the train is still miles away from occupying that first block.
www.lundsten.dk/us_signaling/abs_apb/index.html
Balt: Yes, relay operated, but I am referring to the track circuit current itself, and, as Overmod noted, rapidly repeating relays were suplanted by use of different frequencies' alternating current. Far less expensive to install and maintain.
But of course there may remain areas where there is no coding, just straight ABS. A workable, even reverse-signalling ABS system is possible without individual block coding, and it does require a lot of relays, but they are not rapidly repeating, just responding to the presence or non-presence of a train in the block. Spring-loaded action-delayed ("timed") relays are common. Vapor was a manufacturer that furnished such to EMD, and many diesel-electrics employed such relays in starting circuits. With use of such relays, one can provide information on the direction the train is movoing, not just its block occupancy.
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