OvermodA typical semaphore spectacle has three colored lenses, with a bulb and reflector arrangement behind them. Ideally this hangs by gravity if motor power goes out, and the red light is arranged to be on with the blade as far down as it goes... what happens if the motor power also keeps the light lit is less often mentioned.
Upper quadrant semaphores were weighted on the blade. Lower quadrant semaphores were weighted on the lens holder. Either way, the failsafe was a horizontal blade.
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...
BaltACD In general - there is a progression for the signal indications that get displayed to a train. In its simplest form the progression is CLEAR, APPROACH, STOP. A Clear signal indicates that the TWO track segments beyond the signal have no trains or cars on the track. <SNIP>
In general - there is a progression for the signal indications that get displayed to a train. In its simplest form the progression is CLEAR, APPROACH, STOP. A Clear signal indicates that the TWO track segments beyond the signal have no trains or cars on the track. <SNIP>
This has probably already been addressed somewhere buried in this thread, but just in case, there are far more aspects than just CLEAR, APPROACH and STOP.
In the West, on the former SP, which I was the most familiar with, a flashing yellow signifies "advance approach" which means the NEXT home signal is in the approach position and the following signal after that at stop. This gives the engineer a little more time to react with a heavy, fast moving train.
A flashing red on an absolute signal indicates "Stop and Proceed".
Red over green is "diverging route clear" which means the block ahead is clear but there is likely a permanent speed restriction on the turnout. The engineer has to be familiar with the territory to know what that speed limit is as provided in the "Special Instructions".
Red over yellow is similar, "diverging route approach". Once again, the switch is lined for a turnout but the signal indication is saying that the next home signal is at the stop position.
Yellow over green is "Approach diverging route clear". This tells the enginer that at least the two blocks ahead are clear but, once again, there is a speed restriction on the turnout.
Yellow over yellow is similar. "Approach diverging approach".
Then, I could get into SPTCo semaphore signals but I'm inclined to quite while I'm ahead. :)
Some of the signals in the East, especially on ex-Conrail lines use what's called "Speed signals". Those are a little more complicated and I'm not as familiar with those. Perhaps someone else can explain those.
tree68 Overmod A typical semaphore spectacle has three colored lenses, with a bulb and reflector arrangement behind them. Ideally this hangs by gravity if motor power goes out, and the red light is arranged to be on with the blade as far down as it goes... what happens if the motor power also keeps the light lit is less often mentioned.
Overmod A typical semaphore spectacle has three colored lenses, with a bulb and reflector arrangement behind them. Ideally this hangs by gravity if motor power goes out, and the red light is arranged to be on with the blade as far down as it goes... what happens if the motor power also keeps the light lit is less often mentioned.
You know, I wondered for much of my life as to *WHY* when semaphores had motors and electric lights why they didn't just use colored light signals?
I had this explained to me by an old, nearing retirment age SP conductor on Amtrak's Sunset Limited.
What he told me made sense. "Because they had trouble generating a light that was bright enough to be seen in the daytime." DUH ~ ! This was especially true in much of the West where the sunlight can be very intense. Remember too that there was no electric power out in much of the American outback until after the Second World War. Solar panels were also far in the future.
These signals were powered entirely by lead-acid batteries and the signal maintainers had to go through once a month (or after some specified time period) and change out the batteries then take the spent batteries back to be recharged.
The counterweights and blades were held in the clear position by a rather ingenious locking mechanism that kept the mechanism locked by a minute trickle charge that used very few watts. When a train entered the block, that trickle charge was shorted out and interupted causing the locking mechanism to unlock and release the couterweight flipping the blade up into the most restrictive position. (Red blades showed stop and clear and yellow blades showed approach and clear).
In was ingenious but technology has clearly moved on.
Fred M CainSome of the signals in the East, especially on ex-Conrail lines use what's called "Speed signals". Those are a little more complicated and I'm not as familiar with those. Perhaps someone else can explain those.
As I understand them...
They're actually pretty simple. Per the example I gave earlier about the southbound signal on the SE wye at Deshler - The signal can never give more than a medium clear as the speed on the wye is 10 MPH, and the train will be going through a switch as well.
If you know the plant at a given location, you'll begin to recognize that a given aspect also kind of indicates the route. On the SW wye, a clear (green with a top center marker) means the train will be proceeding straight down the west track to south Deshler, while a green with the upper left marker (approach medium) generally indicates that the train will be taking the crossovers to the Toledo main.
In each case, it's the intended speed (as governed by the plant) that is being displayed, not the route.
Likewise, the signal governing movement from the SW wye to the E-W main (Darth Vaders) can never display a "high green" as the top head only has a red light. The middle head has only two choices, and one of them may be lunar, allowing a restricting aspect to be displayed. I don't recall for sure.
Corrections and expansions welcome...
It's always nice to see a good railroad signaling thread on sites like this.
Was your question answered? There are two main types of questions I get about US railroad signals:
For #1... If you look at my site, you'll see railroads like CSX and NS have multiple pages. Bankruptcies and mergers have brought many disperate signaling systems together over the years. It's often considered too costly to install new, complying signals in the field, and too dangerous and inefficient to re-train crews on new signals for areas they've worked for years. So, for railroads like that, you have to know a bit of the history of the line for which the signal you're staring at came from. Once you know the history of line you're 'fanning, you will know which page to refer to.
Good news is, I do have three more charts in the works I hope to put up when I get them finished.
For #2... The system, generally, does make sense. But it's not a system most people (even railroaders) are going to just work out for themselves. Al Krug did a great job explaning the general basics. Unfotunately his site disappeared, but an archive of it is available here. It's a great read for anyone wanting to understand US railroad signaling. EAch railroad may have a slightly different signaling schema, but the basic concepts are pretty standard.
Railroad signaling is a complex and detailed topic, which is probably why I like it so much. I also find it fascinating how little 8-inch lights can tell a 20 million pound train what to do.
Many years ago, on my first trip aboard the Canadian, a retired CN dispatcher sat next to me in a dome car and he explained the oncoming signals as we proceeded West. At one point he said he thought the dispatcher was just giving the engineer a hard time with the signalling setup.
Jovet It's always nice to see a good railroad signaling thread on sites like this. Was your question answered? There are two main types of questions I get about US railroad signals: What does the signal I'm staring at mean? What? How does this system make any sense? For #2... The system, generally, does make sense. But it's not a system most people (even railroaders) are going to just work out for themselves. Al Krug did a great job explaning the general basics. Unfotunately his site disappeared, but an archive of it is available here. It's a great read for anyone wanting to understand US railroad signaling. EAch railroad may have a slightly different signaling schema, but the basic concepts are pretty standard. Railroad signaling is a complex and detailed topic, which is probably why I like it so much. I also find it fascinating how little 8-inch lights can tell a 20 million pound train what to do.
The following site is basically what you posted but with different formatting.
http://www.mikeroque.com/understanding-railroad-signals/
As with most of railroading, some of my questions were answered here, others by searching. There are too many variations to have them all answered (or for me to know what all to ask).
This goes for all of the rest of railroading. It's been evolving for a very long time so unless a very specific question is asked, the answer will likely be incomplete. Getting questions answered (for me) has been best if I have done enough research to have more than half of the answer. Then, I can be very specific and get an equally specific answer. This site has been very good. I also get answers from some YT channels.
For signals, I don't think I'll ever fully understand them. I think it would require posting photos of a specific signal on a track or set of parallel tracks and ask for all the possible signals and that's simply too much to ask. There are a lot of other things that interest me about railroading and I learn more each day.
Perry BabinFor signals, I don't think I'll ever fully understand them. I think it would require posting photos of a specific signal on a track or set of parallel tracks and ask for all the possible signals and that's simply too much to ask.
That is perhaps the beauty of B&O's old color position lights (CPL's). While there was a specified full complement of lights included by the system, in reality specific installations only had the light heads that were needed.
You can read all about them here: https://railroadsignals.us/signals/cpl/index.htm
Most railroads' signals are somewhere on the web. You'll find that while there may be some different configurations, and the rule numbers are specific to each railroad, but in the end the meanings are very similar.
If you follow a specific railroad, concentrate on learning their system.
One thing I don't have down yet is the modifier that is a flashing head.
All that said - if you remember that red is stop, amber is approach, and green is go, as well as (in general) top head is track speed, middle head is medium speed, and the bottom head is slow speed, you're probably 90% there.
It may be a bit dated, but I have found that my copy of "All About Signals" is still useful in providing the basics. With an assist from a couple of "Rules for Conducting Transportation" in my collection, I can read most signals reasonably correctly.
What can get interesting is figuring out the situation with reverse signalled track governed by CTC.
Action on CSX Old Main Line
https://www.youtube.com/watch?v=8uKqhSTOg_4
Never too old to have a happy childhood!
BaltACDAction on CSX Old Main Line
He's trying to find a steam engine.
Too soon?
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
zugmann PNWRMNM Absent more info we do not know why the yellow is displayed on the top head. Mac Usually, a 2-headed automatic (intermediate) is the signal that comes before an interlocking - sometimes referred to as a "distant signal". So you have there an approach signal, which means: proceed, prepared to stop at the next signal.
PNWRMNM Absent more info we do not know why the yellow is displayed on the top head. Mac
Usually, a 2-headed automatic (intermediate) is the signal that comes before an interlocking - sometimes referred to as a "distant signal". So you have there an approach signal, which means: proceed, prepared to stop at the next signal.
wjstixThe meaning depends too on what system the railroad uses - ABS or CTC or what. Traditionally, two or three head signals were used at interlockings, so say green-over-red meant you were continuing on the mainline while red-over-green meant you were going onto a branchline or taking a siding or going onto some other secondary trackage. In this case yellow-over-red would normally mean you were continuing on the mainline, but at reduced speed - possibly meaning the track block ahead was clear, but the next one was occupied. It could also mean speed was reduced for some other reason related to what's ahead - coming to a station or yard, reduced speed due to a sharp curve, etc.
Signals indicate what's in the rule book. For example, under NORAC, a "green over red" is a clear signal and is rule 281: "proceed not exceeding normal speed". That is it. Usually it means you are staying with the main, but you have to be careful looking for deeper meaning when it isn't there (on paper).
And if you get an approach on NORAC, the block ahead of it better be clear, or we need a maintainer.
Perry BabinFor signals, I don't think I'll ever fully understand them.
First thing to do: figure out whether the RR you're looking at is route signalled or speed signalled. Without that, you'll never understand the signals. If you tell us what piece of RR you're wondering about, maybe someone knows the answer.
The only times (for the most part) that I will see signals is in video (mainly from the US) and I generally have no idea who owns the tracks or signals.
I appreciate the input (even when it may not directly apply to the original question) because it fills in a lot of blanks and makes me think outside my original assumptions.
I will continue to pick up on fine details for as long I continue with this interest (likely for a long time). Sometimes interest is lost when I feel I've learned everything (as much as I want) about a topic. That will never happen with railroads and trains. The more I learn, the more I realize how ignorant I am about the subject.
My observation of most railroad videos, foreign and domestic, it is very difficult to even see the indications being displayed.
One thing I learned from riding the head end of trains during my 51 year railraod career - YOU HAVE TO KNOW WHERE TO LOOK, when it comes to looking for signals, especially when you are riding trains through urban areas - railroad signals have to compete with all forms of lights that exist - traffic lights, street lights, advertising lighting - you name it. If you don't know where the signal is and what it is supposed to be displaying or you can miss it.
The signals are hard to see in videos because the camera adjusts for the majority of the image and not the signal itself. Add to that that some of the signals have lenses that produce a beam designed for viewing at the engineer's position, inline with the tracks and well above ground level.
Perry Babin The signals are hard to see in videos because the camera adjusts for the majority of the image and not the signal itself. Add to that that some of the signals have lenses that produce a beam designed for viewing at the engineer's position, inline with the tracks and well above ground level.
The signal heads actually have a sighting system built in so they can be aimed at the point where the crew needs to see them. Nothing fancy - think "iron sights" on a rifle.
You can see that in play on the southwest wye/transfer at Deshler. During the day, it can be very hard to see that signal from the webcam, since it's pointed so the incoming trains can see it.
While MOST railroad signals are lit with incandescent light bulbs - LED lit lights have a definate FRAME RATE, wherein the the LED cycles many times a second. Many of the video cameras in use today, also have a frame rate in capturing their images. The situation can develop where the frame rate of the camera and the frame rate of the LED go into and out of sync - some times you see the light, some times you don't.
In the following video notice how the crossing flashers show up for a period of time and then disappear for a period of time. With my eyes viewing those flasher, both of them flashed continuously for the duration the included the video clip.
Perry Babin... and I generally have no idea who owns the tracks or signals.
Perry BabinThe only times (for the most part) that I will see signals is in video (mainly from the US) and I generally have no idea who owns the tracks or signals.
If you're watching one of the current crop of rail cams, the description should fill you in on which railroad you are watching. With run through power as common as it is, however, it's sometimes a challenge to figure out who's who just by watching the video stream.
Older videos usually tell who's who as well.
Certain railroads had characteristic signals, a la B&O's color position lights (CPLs). It takes a while to figure all of them out, though.
The cameras are handheld by YT channel owners. They sometimes tell the track owner or something like the XYZ sub but having that information AND the signals is rare.
For fixed cameras on sites like virtual railfan, can anyone recommend a camera location that shows the signals?
Deshler, OH (mostly CPLs, some "Darth Vaders" in view at times) and Leaman Place, PA (Strasburg RR - NE corridor with signals in the distance) are two I know of.
tree68 All that said - if you remember that red is stop, amber is approach, and green is go, as well as (in general) top head is track speed, middle head is medium speed, and the bottom head is slow speed, you're probably 90% there.
Perry BabinAlso, the following is completely confusing. Red on top AND bottom with multiple heads and the bottom head is a single.
Easy peasy.
Each 'stack' is for a single track. The aspects that can be displayed will be covered in the railroad's signal rules. Here's CSX: https://signals.jovet.net/rules/CSX%20Signal%20Rules.pdf
These aren't searchlights - each lamp is a single color. At least that's my experience.
I can't explain why there's red in the top position on a couple of the heads - you'd have to check the special instructions for that installation for that information. It could be that they don't have the usual green-yellow-red set-up due to special circumstances. Regardless - it's the color displayed by the head, not the color's position in the head, that counts.
(Aside - There is one traffic light in Syracuse, NY where the colors are reversed. It's on Tipperary Hill, and as you might discern from the name, here is/was a heavy Irish component to the neighborhood. After several attempts to reset the light to the traditional red on top after local residents reversed it, the city gave up, so green is on top to this day.)
Any given signal will only have the heads necessary to display the aspects for that location. In the referenced image, the left signal will never display anything but red on the top head. That means that the signal will never allow a train to proceed at track speed. The right stack will likely have a modifier (lunar?) in the bottom head. Any unlit head is considered to be at its most restrictive aspect.
The bottom head on left and middle stacks have two lamps. Again, probably modifiers, but with two possibilities instead of one. Again, one would have to know the situation at that particular location.
This is why an engineer needs to know the rules as a whole, and his/her territory.
tree68I can't explain why there's red in the top position on a couple of the heads
Most likely the single bottom head shows yellow or dark -- no need for it to be able to show red. Red over red over red means the same as red over red. I'm guessing the two-bulb bottom heads can light up green or yellow, or be dark.
So why the single top head, showing red? Apparently a train on that track has no full-speed route ahead of it, and red-over-green is the best it can hope for. In other words, the only route ahead of it is thru a 30?-mph switch.
timzSo why the single top head, showing red? Apparently a train on that track has no full-speed route ahead of it, and red-over-green is the best it can hope for. In other words, the only route ahead of it is thru a 30?-mph switch.
That would be my take.
The signal on the SW wye/transfer going out to the EW line includes a lunar in the middle head in order to be able to display a restricting. It's in the CSX signal rules.
One job where where I run, I come off a branch onto the main. Best signal that can be displayed is a slow clear. At that interlocking is a full sized, 3-headed signal - with the top head having only one light (red), middle having only one light (red) while the bottom head can display red (stop signal), steady yellow (restricting), flashing yellow (slow approach), or green (slow clear).
tree68I can't explain why there's red in the top position on a couple of the heads - you'd have to check the special instructions for that installation for that information. It could be that they don't have the usual green-yellow-red set-up due to special circumstances. Regardless - it's the color displayed by the head, not the color's position in the head, that counts.
Like this one here in my neighborhood:
https://goo.gl/maps/djWhLXACoMkLRQAT6
This spur is the remains of an ex-SOU line off Potomac Yard that is now an isolated chunk of NS that can only be accessed from CSX. It is out of service now, as the two customers are gone. The lower head has green, yellow, and red lights and the upper only red. Because of the track configuration beyond that signal, there was no purpose in being able to display most of the potential signal aspects. There was no need or purpose for a yellow over flashing green to mean "approach limited," so why stick a yellow light up there for no reason?
On the following, correct me where I'm wrong. This is at the entrance of the depot. Most trains go straight and only get a red on the top two heads and a lunar on the bottom.
There's no reason for anyting other than the red on top because there will be no track speed at this location. << ?
For the train below, it will not be going into the depot. Initially, it had a red bottom head light and stopped. It didn't get the lunar because it was not going into the depot. This track goes left at the switch. 31° 12.443'N 82° 21.671'W on google earth.
It received a yellow on the bottom head and didn't move. Why didn't it move?
It then received a green on the bottom head and began to move. At about the same time, the gates came down and it crossed the road. What controlled the gates? It seems like the train position couldn't be used since it was already at the crossing.
Why didn't the gates come down on yellow?
On a later train (19:45:30), the gates came down well before the train came into view and the train passes through the crossing on yellow, unlike they di previously.
Does the yellow mean that only one block ahead was clear?
Does the green on the bottom head indicate that the next two signal blocks are clear?
I don't know if these are archived but the date of the video was 2023-07-27 18:11:29. << easier to copy and paste if someone is going to search the archived file.
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