How are signals understood

[JeremyB]

Hi guys

when I go railfanning I'm always trying to understand the signals. What does a signal with three lights mean. They are either all red or the top one blinks green and the middle one is red and the bottom is green, or the top is yellow and the bottom two are red. can somebody explain sinlas to me.

Thanks
Jeremy

[CSSHEGEWISCH]

The Rules for Conducting Transportation of any railroad include signal aspects and their indications for that particular road. Since aspects and indications will occasionally vary slightly from road to road, you might to able to pick up an obsolete rule book at a local swap session. This would at least give you a general idea of signal indications.

[CShaveRR]

Your signal with three lights is the home signal for an interlocking (explained in some earlier threads here...a search will help). All red menas stop and stay. Any other combination of colors will give the approaching train an indication of what he can expect to do at this point...cross over to a second track, take another diverging route, or whatever. Not all of these three-headed signals give the same aspects, because they may cover different types of interlockings.

As Mr. Hegewisch said, these things are specific to the railroad involved, and the rules or special instructions for that railroad are he place to go for their complete meaning. But you can learn a lot by observing. A home signal is controlled by a dispatcher (or tower operator), so if there's something other than red up there, there should be a train coming (it may take a while...). Stick around, and watch what it does when it passes the signal.

[wabash1]

I could give you what the indication of the signals mean but like the others have said that would be on the rail i run. if i go on to some other roads i have what we call a pilot go with me . in most cases it should be a engineer. i have had conductors also but it should be a engineer as he will be the one running. then they will tell us what signals mean and exsplain where we are going.

[BR60103]

Jeremy, if you are in Canada there is a standard set of signals in the rule book. These are also reproduced in the Canadian Trackside Guide, which your local hobby shop should have (new edition every March. PLUG.)
The use of 3 lights gives a lot more instruction to an engineer. A single light might have 6 indications (if you include flashing or solid and 3 colours.) A 3 light signal could give 216 indications (6x6x6).
Example: rule 423 red over flashing yellow over green: "Proceed, slow speed passing signal and through turnouts, approaching next signal at medium speed."
Replace the green with flashing green, and it's Rule 422, and you "...approach next signal at limited speed."

[Anonymous]

I did a quick internet search on railroad signals. Is there a good web site that might answer the question? I got so many responses that it's difficult to know where to look.

There is also a bunch of books on railroad signals availble through Borders.

[Anonymous]

Jeremy, I have to agree with the others that signals are specific to that road. Here in Ohio, CSX uses the color position signal. I live about 5 minutes from one of their signal bridges, and when the signal's aspect is a flashing green, it indicates that the train will be crossing over to the #1 track, heading east.

[jeremygharrison]

I found the following page of Signal links: http://www.8ung.at/smi/asr/ensiglinks.html , which includes links to a couple of sites covering American ssignalling.
What I learnt myself about American signalling (back in the pre internet era!) came from the Kalmbach books 'All about Signals' and 'How to Operate Your Model Railroad' - I don't know if they're still available.

[CShaveRR]

One book that's currently available is Railroad Signaling, by Brian Solomon. It's loaded with color illustrations, and has pages explaining the signal aspects under NORAC rules, as well as for the old Pennsy position lights and B&O color-position lights. Retail is about $34.95, but it'd definitely the most thorough and up-to-date work I've seen on the subject.

[Anonymous]

The PRR used "position lights"....which meant all lights where yellow, on a set of seven lights arranged with a hexagon around the "middle light"......but a problem was that if lights failed.....you could get very different signals. Amtrak replaced most of these with color-position, taking out the central bulb and replacing the hexagon lamps with ones that could be three colors.

Red, yellow, and green are universal colors.....don't know if any railroad uses any others? (although in the London Underground "Lunar White" is also used.....but what about in North America?)

[tree68]

Lunar white is definitely a North American thing, too.

If I recall correctly, traction used red and white.

[Anonymous]

I'm surprised no one has mentioned the differences between absolute and permissive signals. From the standpoint of looking at signals to know if a train is coming, learning the difference between those two helped me tremendously. As many folks have already noted, there are many, many nuances from one signalling system to another. Basically:

Absolute signals are generally found on lines with Centralized Traffic Control (CTC). A signal is absolute when it is sufficient to govern train movement by itself. An absolute signal will always display its most restrictive aspect ("Stop", all red lights), unless the dispatcher has lined up a train. So, if you're on a railroad that uses CTC and you see nothing but red signals, it's a safe bet there aren't any trains around. On the other hand, if you see anything other than red, then there's a train approaching that signal . . . somewhere.

Permissive signals are found on railroads using Track Warrant or Direct Traffic Control. Permissive signals DO NOT have the authority to govern train movements. Trains can only move when given proper authority by the dispatcher (receiving DTC Blocks or a Track Warrant). Generally speaking, the most restrictive aspect that a permissive signal can display is "stop and proceed at restricted speed." Unlike their absolute counterparts, permissive signals often default to the "clear" aspect. In many cases, permissive signals are used simply as a means to show track occupancy. Thus, if you're on a railroad that uses DTC or TWC, and you see a red signal, it likely means that the next section of track (block) is occupied by a train. On the other hand, if all the signals are clear, then the nearest train is at least three blocks away.

I hope that all makes sense and that it's helpful. If it's a little too basic of information, I apologize. I'm new here.

Scott Lothes
Cleveland, Ohio

[csxengineer98]

i learned the signals this way
GREEN.....GO
YELLOW....SLOW
RED..STOP
ANYTHING ELSE AND YOUR NOT SURE..GO 10MPH...LOL
little bit of engineer hummor for you all

csx engineer...

[CShaveRR]

Sxott, an Absolute signal is defined as one whose most restrictive indication is Stop. It doesn't matter whether that's on CTC, TWC, DTC, or any other form of operating system.

Signals that aren't Absolute signals (at least in a block system, or in the case of distant signals for an interlocking) have Stop And Proceed [at restricted speed] as their most restrictive indication (unless modified with some indicator or by some rule so that they can be passed at restricted speed without stopping).

Both CTC and ABS territories will contain some absolute signals, and more signals that aren't, usually just known as intermediate signals. DTC and TWC are systems that place an extra layer of safety above the signals; no signals are necessary for operations like those to exist (if your authority ends at a point that coincides with a signal location, and the signal is clear, you will stop and stay regardless, until given the authority to occupy that trackage).

[Anonymous]

Good points, CShaveRR.

I've heard "Poorman's CTC" described as absolute, DS-controlled signals at sidings or interlockings with ABS in between. I believe permissive signals are also common on mountain grades, denoted by a plate on the mast bearing the letter "G". Is that right? Question on those -- is a red signal in that case still "Stop and proceed at restricted speed" or is it simply "Proceed at restricted speed (without stopping)"?

Here's another question: Much of B&O's Sandpatch grade is directional ABS on two main tracks. I know permission must be obtained from the DS to run wrong-main, but I believe there is a timetable rule allowing operation on the right-main by signal indication alone. I've never been able to find out the details to this, though . . .

Thanks!

Scott

[dehusman]

lothes19 said:
"but I believe there is a timetable rule allowing operation on the right-main by signal indication alone. I've never been able to find out the details to this, though ."

Its called current of traffic or double track operation and it was very common on multiple track railroads. It was used by literally hundreds of railroads over thousands of miles of track at various times.

If you can find a rule book it is usually found in the 250 series rules and is sometimes called "rule 251" territory.

In modern rule books, NORAC still calls it rule 251 and GCOR calls it rule 9.14.

Dave H.

[CShaveRR]

Scott,

Signals with a "G" (or alternatively a "P") on the mast may generally be passed at restricted speed without stopping. You'll never find a "G" or a "P" on an absolute signal!
Their use wasn't always restricted to mountain grades...onCNW we used to have them in places outside the yard, where it would be desirable to bring one train in right up behind the one ahead of it. (There was a collision and wreck at Bensenville as a result of this, but that was a bit before my time.)

[Anonymous]

Many, many thanks for the answers. I've learned a lot about things I thought I already knew! FYI, there's also some great reading on this topic in the "Neophyte Signaling Questions" thread.