How They Work
LED's in Signals
Pictures of Colorlight Signals



Colorlight signals make up the bulk of railroad signals today, and probably every new installation is done with them. 

Most of the class 1 railroads have been in the process of replacing older style signals with colorlights.  The UP, NS, BNSF, and CSX have all been aggressive in the past few years to replace both older colorlight signals as well as other styles they have deemed "obsolete", such as CPL's, PL's, searchlights, and the few remaining semaphores.For instance, when I was in Houston back in 2006, there were at least four locations that were preparing to switch over to new colorlight signals.Around here in the Baltimore area, CSX replaced the B&O CPLís on the Old Main Line many years ago, and just completed last year, a new installation with colorlight signals after taking out crossovers in front of Halethorpe tower (and removing the two B&O CPL signal bridges adjacent to the tower).

The signals at Halethorpe and St Denis MD in 2007 before being placed into service. Way off in the distance is the CPL bridge being replaced.  The MARC train is DC bound, and you can also see the new track going in, which is what prompted the signal project.

Most new installations going in today have what we jokingly refer to as the "Darth Vader" style, where all two, three or four lenses are covered by one hood, instead of the traditional smaller hood for each lens.  While they do look pretty ugly, these hoods are designed to keep snow buildup during inclement weather almost non-existentÖ they also have the extra advantage of keeping light out of the lens from the side more effectively.

The colorlight style of signals can include 1, 2, 3, or 4 aspect vertical (and horizontal) signals, as well as those that are arranged in a triangular fashion (which some of us refer to as tri-light signals).

Colorlight signals come in a variety of case styles, and today are predominantly modularized so the railroads can stack any number of them together to display as few or as many aspects as needed.  In the past the housings were heavy one piece cast iron affairs, which needed a lot of maintenance to keep them from rusting.  Today, most of them are fashioned out of aluminum which tends to resist the elements better.

The photo at the top of the page is of a classic three-aspect signal in Salisbury NC, which, unfortunately, has been replaced by new colorlight sights by Norfolk Southern. To the left is a typical three-aspect "Darth Vader" style colorlight on the Union Pacific.This one is on the UPís track in Mason City IA at the same diamond. For a complete tour of this crossing, check out this page.

  WB single aspect colorlight signal in Bordentown NJ, approach to the wye.




Colorlight signal are versatile, and they can easily be stacked to have more than one head for each signal.A color light signal can be as simple as a single aspect approach signal, such as the one shown in Bordentown NJ (above).Or a signal can consist of two or more heads, each with three or four aspects in each head.Usually though, only one of the heads in a multiple head installation will have more than three aspects, usually.In American signals, the forth aspect would be lunarÖ In other countries, such as Japan, you can have a four or five aspect signal (for instance), with two locations each for a red and/or yellow lens.Even here in the U.S., on transit systems for instance (like the Baltimore Metro system), they use a three lens head, with basically two aspects: lunar white in the middle, and red on the top and bottom, which illuminate together.



This photo is in Doswell VA.  It shows a four aspect colorlight signal, with the lunar "restricting" aspect just above the red.








These two photos are on the CSX in Cumberland MD.  The left one shows quite a mix, with single, dual, and triple aspect heads.  Also, the head in the middle is probably a newer head, for it has a narrow background compared to the other two, and it has the Darth Vader hood.  Even though it looks like a newer installation because of the pole, this was probably on the Western Maryland and they re-used the top and bottom heads, as the WM was a big believer in using the wider backgrounds.  The pix on the right is on a three track ex B&O main in town and shows the use of red in the top position.



Although red is generally associated with the bottom position of a colorlight signal head, there is nothing to say that it has to be that way.The Baltimore Light Rail system and MARTA in Atlanta are two examples where they placed red on top, the same as standard traffic lights, so the operators wouldnít get confused.The Minneapolis Light Rail system started out that way, and then changed over to the conventional railroad standard of having red on the bottom.There are still many railroads, that in a multiple head signal, will employ red on the bottom of one head, and then be on the top of one of the other heads as seen above.




Interestingly enough, the majority of railroads employed colorlight signals in the vertical position.The only example I can think of offhand that didnít, is the CNW, which used horizontal signals.Again, some transit systems would mount the signals wherever they could in the case of close clearances, and I saw many a signal on the New York Subway system where they were on an angle to closely follow the curve of the tunnel.  On the left, is a photo of a signal at the Railroad Museum of Pennsylvania in Strasburg PA - the bottom head is mounted horizontally, altho I don't think the signal is from any particular railroad.

There is a separate page to cover the "tri-light" style colorlight signals: click here.


According to Brian Solomon in his book Railroad Signaling, colorlight signals made their first appearance in the East Boston Tunnel in 1904.  In 1905, they appeared on the Long Island RR, and in 1906, on approaches to New York Centrals Grand Central Terminal which was in the process of being electrified. They first showed up in tunnels because high brightness was not a requirement.

For more reading: http://books.google.com/books?id=TISRZNN0sCMC&pg=PA45&lpg=PA45&dq=%22color+light+signals%22+history&source=bl&ots=-zn7k_r8Pt&sig=gjS-4HqJNheX-80SRaqBcBQL3U0&hl=en&ei=yM-QSrf1IdWplAee1eS0DA&sa=X&oi=book_result&ct=result&resnum=1#v=onepage&q=&f=false

Colorlight signals had to wait for the introduction of a convenient, if not cheap and reliable light source: the incandescent light bulb.According to most sources, this didnít happen until 1914, when a concentrated filament bulb was developed, giving the color light signal an acceptable sighting distance.  Once the signals could be seen for 4,000 feet, during the day, signal designers started using them all over the place.

The colorlight signal also had to wait for advances in lens technology AND clearer lenses to be developed.

Advantages of the colorlight signal over other forms of signaling includes having the same indication during both days and nights, and no moving parts, making maintenance way simpler.

US&S developed the TR-2 style colorlight, where the lenses were arranged in a triangular fashion, in 1924.  They are nick-named tri-lights by some.  Placing the signals in this format reduced the effective size of the signal, mostly in height.

Itís interesting to note, that by this time, Corning had done research into lens color visibility, and had recommended the use of green-yellow-red, over the then popular white-green-red format in wide use.Corning did this research in 1906-1908.For a mostly complete signal timeline, check out: http://www.railroadsignals.us/basics/timeline.htm .

FYI, according to Solomon, the automobile traffic light was adapted from the colorlight railroad signal.

How They Work

Colorlight signals are simple in concept and design.  There really isn't that  much to them.†

For each color of a colorlight signal, there is a bulb as a light source.In some instances, such as rapid transit signals, there may be two lamps for each aspect, one acting as a back-up in case the main bulb failed.Most bulbs operate off low-voltage AC, such as 8, 10, or 12 volts, and utilize an automobile sized bayonet base lamp which can have either a single or double contact base.Again, in certain instances such as transit applications, the bulbs will operate off 120VAC, and utilize a standard size Edison base light bulb.Most bulbs are mounted vertically, and have a pre-focused filament, which means the signal maintainers should not have to re-align the signal every time a light bulb is replaced.Bulbs are also rated for a higher number of hours, which they do by making the actual filament voltage a little higher than the actual operating voltage, but this also means that the bulbs are imperceptively less white than if they operated at full voltage.The lens coloring takes this into account.

The light from the bulb is usually focused by a pair of lenses, usually referred to as a doublet.One of the lenses is colored, and itís usually the inner lens.The inner lens is almost always a Fresnel lens, which has the advantage of being able to focus the light beam, but not being as thick as a regular convex lens.  The outer lens is often a Fresnel, but not always... Some are clear lenses, and others have a special pattern to shape the beam in a specific manner according to the installation and what the signal designers are trying to accomplish.  For instance, on the CPL dwarf above, the two lenses work together to produce a narrow beam horizontally, but it maybe has a 90 degree viewing angle in the vertical plane, since they are mounted at ground level and need to be seen from a distance as well as close-up.

Most, but not all signals, DO NOT employ a reflector behind the bulb, and colorlight signals are no exception.This is so incoming light, whether it be from an approaching engine, or from the sunlight, does not get reflected back out and make the signal appear illuminated.

The signal on the left is one from the New York City Subway system I picked up at the train show in Gaithersburg MD several years ago.  Notice that it doesn't have any hoods since it was used in a tunnel.  It operates off 120VAC.  The searchlight and dwarf CPL are running off a 12V garden transformer.

Itís interesting to note, that in the old days on the Pennsy, the signal maintainers had their hands full at dusk and dawn, going out to adjust the taps on the transformers to adjust the brightness on the bulbs so they maintained a more or less constant brilliance in relationship to the sun.This must have been fun in the bad weather.I know they did this on the Position Light signals, but I am not sure they did it for other types of signals.

LED's in Signals

In recent years, there has been a trend to replace the fairly reliable incandescent lamp with LED lamps.Iíve seen some of the Amtrak PCLís on the corridor around Wilmington DE using LEDís, even in the pedestal signals at the station.

There are a couple of "tri-light" signals in Havre de Grace MD that for years have been using LEDís.

So far, the railroad LED lamp units seem to be more reliable than their automobile counterparts, which personally, I think have a bad track record considering their cost.Drive around any municipality that uses LEDís in their traffic lights, and you will see what I mean with many of them having bad sections in them that are not illuminated. 

Below is a small sampling of LED signals being used today.....

The two photos above are on the MARTA Metro system in Atlanta, notice that they use traffic light placement and further back in the yard, two aspect signals are used.  I also understand they have a few four aspect signals with lunar white, but I have not come across them.  MARTA uses nothing but LED's.

Above is a "tri-light" version of a colorlight signal which can be found on the Northeast Corridor in Havre de Grace MD, replacing a set of SB position light signals as the trains came off of the Susquehanna River bridge.

Although not a colorlight signal, here in Wilmington DE we have a pair of Pennsy Pedestal signals on the NB side of the station.  If you look at the two signals, you will notice that the left one is showing us two lunar lights, while the one on the right has a combination of LED lunar bulbs on the bottom, and regular incandescent lamps on the top.

Here we have a newer installation of color light signals in Charlotte NC on the Lynx Light Rail system.  Like MARTA, they are all LEDs.

Pictures of Colorlight Signals

Blacksburg SC
Shelby NC
Doswell VA
Goshen to Waynesboro VA
Durham NC
Gaithersburg MD
C&O Signals in Kentucky
Galveston TX
Gastonia NC
Houston TX, Tower 87
Lorton VA
Point of Rocks MD
Salisbury NC
Buffalo NY

For additional pictures, check out the links below

Blacksburg SC

A two head colorlight signal in Blacksburg SC.  Photographed by Mike Falls. 
The photo on the right is a composite of the aspects he has seen on the signal.  Thanks Mike.

Shelby NC

Another picture sent in by Mike Falls of a signal at a siding in Shelby NC... There's one of these at both ends of the siding.
It's on the CSX, a former Seaboard Air Line track,
And the turnouts are DTMF controlled.
These might be the first horizontally placed signals installed since those on the CNW?  Thanks again Mike!
It's at N35 18' 52.7"  W81 36' 24.9"

Doswell VA

These photos are in Doswell VA at the ex RF&P/C&O diamond there - it's all CSX now.   The "big" photo is the backside of a set of signals for SB trains heading into Richmond, before it hits the diamond here.  It shows how signal designers will mix heads when only one or two aspects need to be shown.  The thumbnails are of a new installation on the C&O track, with a CSX freight heading westbound out of Richmond.  CSX still runs left hand traffic, as the RF&P did, hence the signal on the "left" capable of more aspects.  Back in 2007, CSX installed new signals at most location at the diamond, except for the one on the left - they are Safetran modularized color light signals.  I believe they did this because they moved a crossover several hundred feet to the south.  The telephoto pix on the right is taken from the overpass just down from the 95 exit.  The freight on the diamond is SB on it's way to Richmond.  For more pix and a guide to the diamond at Doswell, click here

Goshen to Waynesboro VA

A great set of ex C&O US&S colorlight signals between these two towns.  Photos are by Joseph Norman who is documenting signals in Virginia near where he lives and works.  These are currently on the Buckingham Branch Rwy. 
For the complete set of photographs, check out:
Also check out his pictures of NS's Winston-Salem District at: http://pumpkinvine.wordpress.com/signals/

Notice in the set that there is a cantilever bridge signal where there may have been two tracks at one time; a bracket post signal with a doll post because there was a second track for which the doll post indicates; and notice that there are several dwarf signals on short masts to increase visibility.  Nice set of pix!  There are more of his pictures on my N&W CPL page.





Durham NC

These are fixed approach signals along S. Hoover Road, just off Angier Ave.  It's for an NS branch line that goes up to Oxford and Henderson.  The signal is on the top, or north end of a wye, west leg.


Gaithersburg MD

Photos of a relatively new installation on the CSX in Gaithersburg MD (these pix are from August 2007) which illustrates several points about new installations:  The modular construction of the signal housing can be clearly seen in the middle photo, and on the left, it shows how signals no longer have to be located to the right of the track due to relaxed FRA rules on signal placement.

C&O Signals in Kentucky

RSUS is proud to present a series of pictures from Chase Gunnoe, who has been making an effort to go out and document the remaining C&O signals near where he lives on the CSX's Kanawha Sub-Division, east of Russell KY.  All photos are copyrighted by Chase and used with his permission.

  EB CSX freight at Big Sandy Junction, MP 513.5, Catlettsburg KY 1/13/2010

  Another shot in Catlettsburg KY at the Big Sandy Turnout "Floodwall"

  EB ballast train at the Clyffeside signal bridge in Ashland KY, MP 516.4  5/9/2010

  Another shot of a westbound in Ashland at MP 518.6 with the 19th St cantilever in the background  1/9/2010

  Eastbound GMRS-1 at the intermediate signals at MP 515.5, in Ashland  3/9/2010

Galveston TX

A dual head colorlight signal on the north end of the bridge going over to Galveston Island, shared by BNSF (ex ATSF) and UP (ex SP).

Gastonia NC
A classic Signal Bridge



This signal bridge in Gastonia is located just off interstate 85 at exit 19, Ozark Ave.  South from 85, Ozark turns into Long, keep going south to Rhyne St and take a left, and another left at the tracks, go north along the tracks till you can't go 'no further.

Houston TX
Tower 87: Englewood and Settegast Yards

These two signals, located only a couple hundred feet from each other, illustrate what engineers have to put up with today in the world of "mega-mergers", as they both show restrict.  It's all Union Pacific now, but it used to be UP and SP not too long ago.  For more pictures of this junction, click here

Lorton VA

Just on the other side of the road from the Amtrak Autotrain terminal are these signals, easily accessible of Gunston Cove Rd and I95.

The Autotrain siding comes out onto the NB mainline track, as CSX still runs the RF&P way, reverse traffic.  The first crossover to get it on the correct side isn't till Featherbridge, below Woodbridge, almost 5 miles south.  The intermediate signal is typical of the new installations along the RF&P.  The cantilever bridge holds signals for the Amtrak Siding, and for reverse SB traffic.  The picture on the bottom right shows a medium clear for the Autotrain.  The Autotrain leaves each terminal at 4:00pm, and arrives at 9:30am the following morning, with a run of 855 miles between Lorton and Sanford - it goes thru Doswell (above) around 4:45 or so (SB). 




Every year, my friend Jim Mihalek from Minnesota treks to Ohio where he grew up to document the signals there.  Here are some pictures from those efforts.  These signals are all on the ex-NKP line that is now the NS Lake Division.

Right photos at Shinrock, mp232.  Photos taken 2008
The left photo is was taken at Leavitt Road, Lorain, Ohio (Ohio 58-mp B212).  The second photo was taken at West End Shinrock.  The two photos on the right are taken at Overlook Rd., Vermilion, Ohio at KM (mp B218).

East End Avery, which is easily accessible off Hoover Rd, via Milan Rd and E. Mason Rd.  Milan is exit 118 off the Ohio Turnpike.  The west end of the siding is off Kelly Rd.  We're about 45miles west of Cleveland on the NS, ex NKP, mp235.  Photos taken 2008.

Thanks to Jim for his pictures and Steven L. Klement for the detail information.

Point of Rocks MD

Well entrenched in what used to be hardcore B&O CPL territory is this fairly new colorlight installation at the ex B&O station, now used by MARC.  Note that red occupies the second position up, as contrasted by the 4 aspect signal in Doswell, shown above.
For more pictures from Point of Rocks, click

Salisbury NC

This WB/SB color light signal is located adjacent to the station in Salisbury, just down the road a ways from the Spencer Shops Museum.  The signal is GRS, the base is by Modern Industries.


Buffalo NY
A couple of outbound Colorlight Signals at the east end of SK Yard





Links Within RSUS

This is a partial list of places elsewhere on this website where you will find pictures of colorlight signals.

Albert Lea MN

Berea OH

Tower 85 in Houston TX

Pierce Junction in Houston TX

Mason City IA

Signals of the Houston Light Rail System

Signals of the Minneapolis MN Hiawatha Light Rail System

Signals of the Charlotte NC Lynx Light Rail System



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NEW: 10/12/2006
Last Updated: 22-Jun-2014