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?
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.
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.
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.
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.
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.
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.
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”.
You might want to look for the book “Classic Railroad Signals” by Brian Solomon on Amazon.com. It is written for the layman (like me!) and covers topics from early semaphores to speed signaling and moving block signaling.
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.
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.
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.
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.
Brian, the wastbound signals are home signals for the Grace control point. If anything other than red is showing on any of the heads (even a flashing red), it means there’s eastbound action.
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.
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 O