# HOW MANY COLORS?



## John J (Dec 29, 2007)

How many colors are there on a signal tower?

Red Yellow Green?

or just Red and Green?

Is there a proceed with caution signal?

Are there three colors only in certian areas/ 

JJ


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## Scottychaos (Jan 2, 2008)

There is (and was) a huuuuuuuuge variety of signal types mounted on towers.. 
different railroads had different types of signals. 
from everything I have ever seen (on East coast and North-east railroads) they all have green, yellow, and red signals in the past.. 
although now I think CSX is only using red and green! I havent noticed any yellow on modern CSX signals.. 

in the past, some had semaphore signals, others had "target" type signals..semaphores are basically extinct now. 

the differences are very railroad-specific..I dont think there is (or has ever been) any nation-wide standard. 

if you are modeling a specific prototype, you can use their practice as a guide.. 
if you are looking for something more "generic" I would go with a basic 3-light target signal.. 

most modern signals are a single light target signal, that has green yellow and red, or possibly just green and red. 
http://www.danstrainyard.us/webphotos/ns/SD40-2/NS 3430 Alexander 1 17 07001.JPG 

or semaphores!  
personally I have always been a big fan of semaphores.. 

http://paulpratter.com/biography/alcofa2.jpg 

PRR, naturally, had their own design! 
http://upload.wikimedia.org/wikipedia/en/1/18/NS_Buffalo-Line-Signal-304-3042-APPROACH.jpg 

so the answers to all your questions are "yes"..  

Scot


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## Totalwrecker (Feb 26, 2009)

I seem to remember all white signals too that used 3-4 lights in a row, vertical was go and horizontal was stop. 

John


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## pinewoods (Jan 20, 2009)

Check this one out, one of my favorites 

http://broadway.pennsyrr.com/Rail/Signal/aspects_us_cl.html 

The most common colors are red, yellow and green. In older signals white and sometimes purple were used. Currently white is typically used for a 'restricting' indication which tells the crew to proceed at a speed slow enough to stop short of another train or problem with the track. 

Currently yellow usually means 'approach', indicating that the next signal down the line is at 'stop' and the train should be slowed prepared to stop at the next signal. 

The PRR had a caution aspect which was a diagonal row of amber lights with a single lamp below. 

I like semaphores for large scale because the indication can be seen from any vantage point, you don't have to be on your train.


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## Tom Parkins (Jan 2, 2008)

White is also on signal heads too. Green with lunar white on top = proceed. 

Again way too many variations to address here. Consult your local railroad on the internet for signal displays. 

Tom P


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## Andre Anderson (Jan 3, 2008)

John,

Why the question? The answer will will help us to answer the original question. 

Andre


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## John J (Dec 29, 2007)

I was at a swap meet here in Phoenix at the Baptist Church. I saw a Lionel singal tower from O guage layout. I was thiniing of buying it and use it at a model to make some G scale signal towers. 
Then I saw some Pictures from the Convention in Washington and saw some had three lights some had two and some had one. I was just wondering.


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## jgallaway81 (Jan 5, 2009)

John, it all depends on what you decide to use...

Your first choice would need to be what style of signals do you wish to use: Mechanical or Optical - (if you don't want to actually place signals, you could always say your line uses cab signals without waysides, although there are usually still wayside signals at interlocking plants)


Mechanical: 

1) Ball on a string: This is exactly what it sounds like. A large red ball was hooked to a string that was suspended from a cross-arm. As far as I know this style was never used for the automatic block signal system. In the lower position, it meant the train needed to stop at the signal. In the upper position, the train was permitted to proceed. In the upper position, it was known as a (get ready for this highly technical term) "Highball" signal. It is in fact, where we get the term "highball" from.


2) Semaphore: This was a mechanical arm operated initially by a signalman before being equipped by a motor and actuated by the automatic block system. It's position, relative to vertical, is what told the engineer how to operate the train. A single head signal could display the equivalent to the modern "Clear" with a vertical arm; "Approach" with a diagonal arm; and "Stop-and-Proceed" with a horizontal arm; (For a definition of these signal "aspects", feel free to search for a copy of the NORAC rulebook via google). Originally, these were built so the signal dropped from Stop to Approach to Clear. The trouble was that if something went wrong, the signal could display an indication better than it was supposed to: if weighed down with snow and ice, the arm could be pulled down from "stop" to "approach", even though the block was occupied by another train. Eventually this was changed so that the Arm swung from vertical, down to approach, down to stop/horizontal. So, even if the block was clear, the snow would force a more restrictive signal. This is where the idea of "fail safe" was born for railroad operations. Eventually, before they were phased out of operation, as many as three semaphores could be stacked into a single signal, providing a much more informative indication. The most well known signal that uses all three heads would be a Horizontal/STOP over a diagonal/APPROACH over a vertical/CLEAR. This signal today is displayed as a red over a yellow over a green and is called a Medium Approach Medium. (For once, google let me down... I could only find models of this style semaphore)


Optical:
3) Semaphore with lights: For the most part, this signal was as used above, but also included a lighted colored lamp to provide signal indications at night. At this time, science has not managed to produce an amber glass lense capable of being seen a mile away. Because of this, railroads utilize the colors Clear, Green and Red. Often these colored lenses were mounted in the counterweight of the semaphore arm, and were arranged so that the correct color lense was illuminated by a single light as the arm moved through the quadrant, ie: when the arm was diagonal, the green lense was lit.

_*Between 1906-1908 the Corning Company's research department finally managed to produce an amber lense that could project a beam of light the require mile distance. With this advancement in optical technology, the stage was set for the next hundred years of railway signal systems.*_


4) The main trouble with semaphores was the mechanical arm. Because of the limits of small motors of the times, they were very susceptible to being pushed out of position by inclement weather. Also, in bad weather, the signal arm was hard to see, requiring the engineer rely on the night-lights. Additionally, in 1913, the Pennsylvania Railroad began its massive electrification program. Within months management knew the catenary was causing difficulties for engineers trying to read semaphores. By 1915 all the parts came together, the amber lense, a conical fog-penetrating focusing lense, and concentrating-filament lamp, and the PRR debuted its "Tombstone" Position Light Signal. Originally, these signals used rows of four lights "pivoting" on the second light (counting left to right on a horizontal signal) to simulate the arm(s) of an upper-quadrant semaphore. This provided the most safety of any signal system ever to be developed except for the coming PRR advancement of in-cab signaling. The lights provided all-weather visibility, the arrangement meant that anyone who could read semaphores could also read the position lights. Additionally, the number of lights per aspect meant that even if a couple of bulbs blew simultaneously, the engineer could still read the signal. Eventually these 4-light PLS's were modified to reduce the number of bulbs to 3 per line, and the pivot point became the center bulb. This is the Position Light signal system we all know of Pennsy fame.


_*In 1916, the Pennsylvania Railroad and the New York Central finally change their rulebooks to reflect the change from white to green for the proceed indication. It is at this point the the universal red-yellow-green color system is adopted. 
*_

_*While the position light system has several advantages to semaphores, its design and implementation has a couple of drawbacks as well. The number of lights means you draw a lot of power, especially with the much less efficient bulbs of the day. Further, (at least today) if a bulb blows, the FRA requires that it be replaced immediately citing safety concerns. This means that a signal maintainer needs to be called out immediately. Also, because the signal system was designed nearly a century ago, few modern technological implementations have been used to update the system, though by no means does this mean that it couldn't be done.*_


5) Searchlight: Citing the use of the projection lamp and for penetrating lenses, and the use of a single bulb in night-time semaphore lamps, design work began on a single bulb signal that used electrical "snap" servos that moved colored filters into place between the lamp and lense. The filter system was counter balanced such that without any power application, the filters would default via gravity to the red or "stop" indication, again demonstrating the fail-safe principle.


6) Color-Position Light: A compromise to both parties. This system duplicated the positions of the basic position lights, however, the center bulb was removed and the remaining bulbs were color coded. This provided extra security to a bulb burning out, as well as allowed colors to help transmit the indications further out. In closeup views, the positioning helped to reduce the danger of a "phantom" indication caused by reflections from light sources outside the signals. Further out, where reflection must be dead-on in order to reach the train crew, the colors told the indication. At that distance the individual lights had a tendency to blur together anyways. This system is still in use on Amtrak's "North East Corridor (NEC)".


7) Basic Color Light System: While the above system had the simplicity of a single bulb, it had the drawback of a electromechanical system to operate the colored filters. Many railroads decided that the added complexity didn't outweigh the cost of multiple bulbs. So, the three-bulb "color-light" signal was developed. This had the benefit of no moving parts, but had the downside of multiple bulbs. Also, if one bulb went out it created a condition where the indication that was supposed to be displayed was unknown. Now railroads had to modify their rulebooks to take into account a dark signal. Overall, railroads eventually came to the decision that this system had the greatest benefit-to-cost ratio. Slightly modified, this system is still in use today.

8) Hypothetical: LED Color-Position Light Signals: -->This is a signal system of my own design.


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## San Juan (Jan 3, 2008)

The old Lionel signal tower is nice. 

We have one for our O scale layout. You can see it on the right side of this photo:











It only comes with two lights (bulbs) per side, one red one green. Most towers like this would also likely have a third color (yellow), tri-light. But there are signal towers that have single head lights called searchlights that can display various colors in one signal head. But this isn't exactly what the Linoel signal head looks like either.


Prototype signaling can get extremely complex. Just look at some of the responses you've gotten already. 


So to answer your question, there can be any number of colors. No one true answer as it depends on various factors including the track arrangement, railroad, era, and signal manufacturer. But a very simple answer would be three main colors; red, yellow, and green with the occasional oddity Lunar aspect (see the other responses above).


If you'd like to see some railroad signaling practices, take a look at this link:

Railroad Signals 



One thing I can tell you about the Lionel signal bridge is if you want it to display a green aspect over red (most common for most railroads) instead of the Lionel traffic light set up of red bulb over green bulb, all you have to do is swap the bulbs. So simple but I actually thought about reversing the signal head before I realized all you have to do is swap the bulb location


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