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►RAILROAD SIGNALS of the U.S.
A PRIMER ON
AMERICAN RAILROAD SIGNALS
Signals Common in the United States Today
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CHAP 1 -
Introduction
CHAP 2 -
Signals Common in the United States Today
CHAP 3
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Glossary of Signal Terminology
CHAP 4
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Reading And Interpreting
Railroad Signals 1
CHAP 5
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Reading And Interpreting
Railroad Signals 2
Prior to 1900, signal styles were a lot more individualistic, and could vary widely from railroad to railroad. More and more today, the American signal scene is finding color light signals, where there was once a wide array of styles to feast on. You could still find semaphores everywhere into the 70’s, now they are rare. The B&O CPL’s and Pennsylvania PL’s were plentiful east of Chicago, however, their numbers today are rapidly dwindling. There was even a lone ball type signal that made it into the 1990’s in New Hampshire. Operating wig-wag crossing signals can still be found, and to even a lesser extent, rotating banner signals (although I am not aware that any of them still have the stop sign in place). You could even find smashboards and tilting targets being used into the 90’s. The same goes for switch lanterns - they used to be common place, but try to find one these days - they have almost all been replaced with reflectorized stands.
According to Alstom, signaling on American railroads was introduced as early as 1857, but extensive installations were not made until 1900 when railroad management realized the benefit signaling could provide to expedite traffic movement.
As already stated, the general trend of late has been towards the use of color light signals. One notable exception is the Northeast Corridor between Washington D.C. and New York City, where Amtrak has kept the Pennsy PL’s, but colorized them. This is probably for the same reason that the Pennsy developed the PL’s in the first place – limited room to mount signals so they could be seen between the mess of overhead wires and support structures. The Norfolk Southern, in former N&W territory, has also been slow in replacing their CPL’s.
Many of the older signals were complicated mechanical mechanisms or assemblies such as semaphores, B&O CPL’s and Pennsy PL’s. Semaphores taken down during the 40’s, 50’s and 60’s were replaced by searchlight signals or color light signals, and many of those searchlight signals are today being replaced with color light signals. Why replace when the old signals work fine? My guess would be high maintenance cost, although rusting equipment and hardware could be another. And if you are going to replace something, (logic dictates) you might as well do it with something new. Although rare, a fully loaded B&O CPL uses 14 bulbs, in as many individual housings, in contrast to three stacked color light heads (housings) using a total of eight or nine bulbs in the three heads. It’s a matter of simple economics in an industry where they can tell you how much it costs to blow the horn at a grade crossing. Railroads, like any other profit making business, try to contain costs (especially on overhead items such as signals), otherwise, steam engines would still be common place.
Learning the difference between the styles is not difficult, but trying to figure out if a searchlight is a GRS or US&S head, is a little more difficult. Hopefully, this primer will answer some of the questions you may have. To differentiate the signals I am talking about here, from other signals on the railroad, we often refer to these as wayside signals.
The majority of
signals in the United States today are:
Semaphores
Searchlights
Color light and Tri-lights
Position light (PL)
Color position light (CPL) and PCL (position color light)
(semaphores just barely make it onto this list)
The major
manufacturer of signals are:
GRS (General Railroad Signal – now Alstom)
Safetran
US&S (Union Switch & Signal)
Harmon (GE)
Western Cullen Hayes
WRRS (Western Railroad Signal).
Semaphore signals - They were once the mainstay of American railroading, they are becoming increasingly rare. http://www.semaphores.com does a pretty good job of keeping you up to date of where the last survivors are. Semaphores used a combination of two technologies to convey information to the engineer. During the day, a board approximately three feet long was put into different positions by some sort of actuating mechanism, be it "armstrong" (purely hand operated mechanical), pneumatic, or electrical, or a combination of those technologies. During the night, the same part of the signal that the board mounted to, the spectacle, contained two, three, or four colored lenses, which would rotate in front of a stationary light source. …..Semaphores, we all love them, but due to their mechanical complexity, have given way to simpler devices such as the searchlight signal or color light signal.
Semaphore signals on the New Haven, in the Bronx, judging from the apartment buildings in the background.
Searchlight signals - Searchlight signals placed a miniature like semaphore mechanism inside a small housing. Three, roughly 1 inch diameter lenses were placed on a small spectacle, or vane. They were used by many railroads, with the big exceptions being the Pennsy and the B&O. The current mainstays of this type are the Alstom (GRS) SA-1(5), and the US&S H-2 and H-5 (6). Even searchlight signals today face the same demise as semaphores and position light type signals. They are being phased out in favor of the color light signal, again, because they are simpler to maintain.
A couple of classic
searchlight signal installations at the same location in suburban Atlanta, these
are of the US&S variety. The easiest way to tell is by the hoods.
A couple of dwarf
searchlight signals in Buffalo NY, on the former New York Central (now CSX).
These are GRS units, the giveaway being the hoods - notice the difference in
their shape from the US&S hoods above.
Color light signals seem to be the most prevalent type in the United States today (this is just a personal observation). They are simple in design, and are nothing more than a housing with a separate chamber and light bulb for each aspect to be displayed. Railroads like them because they are simple to maintain - no moving parts. Older models were a single housing with a separate compartment for each bulb. Some newer designs are taking the modular approach, and can be customized with any number of aspects on one head. Another trend is towards the use of aluminum and plastic, where steel was once the only choice (FYI - you can’t find a traffic light made today that isn’t plastic).
Three color light
signal installations -- On the left is a newer installation on CSX's RF&P
division in Lorton VA, just south of the Amtrak Autotrain terminal.......
In the middle is a CSX two head color light signal in New Castle PA,
replacing a CPL on this former B&O line..... On the right is a two head signal
on the NS in Cleveland OH.
Tri-light signals are an adaptation of color light signals, where the positioning of the lenses are in a triangular pattern, giving the signal a maximum of three aspects.
Tri-light signals in
Berea OH, slightly to the west of Cleveland. Both CSX and Norfolk Southern
use tri-lights at this location, which is kind of unusual. NS has, so far,
kept the old support structures for their signals, making for interesting signal
shots compared to the dull and boring aluminum structures common in
installations today. The CSX tracks are on this side of the tower.
This is great railfan spot where the NS and CSX come together for some good
action, and is a favorite spot with the locals.
Position Light signals (PL’s) were developed by the
Pennsylvania Railroad. They were developed to overcome the disadvantages
of the semaphores. PL’s were used by the Pennsylvania Railroad and
associated railroads, such as the Long Island RR, and the Norfolk and Western.
The Pennsy also came up with two associated signals, the PL dwarf signal and the
Pedestal signal. The dwarf could only display four aspects, but the
Pedestal could display everything except for the circle and “X”. The
Norfolk Southern, now that it has acquired 60% of Conrail, has been busy
replacing the PL’s with color light signals.
During the 60’s, the N&W “colorized” their PL’s, so they look similar to the B&O CPL’s from a distance. So far, NS has been content to leave most of the N&W CPL’s alone, but you can find evidence of replacement here and there, such as in the downtown area of Roanoke VA.
This PL signal is located in Mapleton PA on signal bridge 1932.
Color Position Light, or Position Color Light? With the next two categories of Position Light signals, there exists some confusion in the industry as to what to call the colorized version of the Pennsy Position Light signals. The B&O CPL’s have always been called CPL’s. However, the signals used today on Amtrak signals on the corridor between DC and NYC (as well as the signals on the Norfolk and Southern in former N&W territory), are adapted Position Light signals. Amtrak maintainers call theirs Position Color Light signals. Another term that is applicable is Colorized Position Light signal. I guess when a railroad adapts a Commercial Off The Shelf, or COTS, model, they can call it whatever they like.
The effectiveness battle between position type signals such as the Pennsy PL's and the B&O CPL's continues till today, although it is a moot point since they are all being replaced in favor of color light signals. The Pennsy went with all yellow signals because they said the signals could be seen through most forms of inclement weather better than anything else. The main difficulty with an all yellow signal is viewing it from a distance and not being able to discern the aspect it is displaying, and therefore, making the engineer wait until he was closer to the signal in order to see what it was telling him. Many people consider the B&O CPL the better choice, even with the odd form of marker lights used to modify the meaning of the aspect displayed on the main head. From a distance tho, you could readily tell the difference between the colors on the B&O 's lights.
Color Position Light signals (CPL’s) were developed by the B&O Railroad. They went off in a slightly different direction from the Pennsy, but they still wanted to electrically duplicate the semaphore action. Keep in mind that these efforts were in the "good-ole-days" when the railroads had real engineering departments that actually designed and made things. So they decided on using a series of colored lamp pairs for each aspect, arranged in the same horizontal to vertical fashion that semaphores used. Interestingly enough, B&O CPL’s were chosen to be used on the joint trackage into Washington DC Union Station. The dwarf version , if so fitted, could display ALL of the aspects of its full size brother, and they are the only dwarfs that can claim this. The B&O Railroad museum in Baltimore has the only “full” dwarf I have ever seen. Over the past few years, CSX has stepped up its efforts to replace the CPL’s (:-), and SIRT announced in 2005 that it would be replacing its remaining CPL’s. Get pictures of them while you can!
Both sides of the same
CPL location at the Gaithersburg fairgrounds in suburban Washington DC.
Both tracks are signaled thru here for bi-directional operation.
These eastbound CPL signals are for northbound traffic at ROSSVILLE in the Rosedale section of Baltimore County, NE of Baltimore. On the other side of these signals, the track goes to a single line for it's trip up to Wilmington DE. According to the B&O map, they are absolute signals at this location, as well as the one for facing traffic adjacent to the train.
A couple of dwarf CPL signals at Bailey's wye in Baltimore MD, just south of Camden Station.
Position Color Light signals (PCL’s) were an adaptation of the Pennsy PL signals, where they colorized the signals. So far, Amtrak has been content with keeping them around, altho they have been experimenting with LED's south of the Susquehanna River bridge. To accomplish the change from PL to PCL, they had to eliminate the center head. They had to do this, because each head was capable of only displaying one color, or aspect, and that wouldn't work when the signal had to display "green", "yellow", and "red" aspects. I guess, since the N&W colorized their PL's, we have to call them PCL's to, but there is no general agreement on whether they should be called CPL's or PCL's.
Amtrak PCL's at the
south end of the Halethorpe MARC station (SW suburban Baltimore), and a pair in
Wilmington with LED's..
This photo, taken in
downtown Roanoke VA, illustrates the N&W's adaptation of the Pennsy PL signals
into colorized versions, including the dwarf version. The N&W kept the
center light in the lower head, so it could be used to display their stop
aspect. The nice thing about these signals, is that even with a bulb out,
as with the right most signal, you still have two red lamps lit. Notice
the dwarf's have been colorized also.
REFERENCES:
1 SA-1 reference
2 H-5 reference
3 http://www.railroadsignals.us/cobo2d.jpg - Scan of C&O/B&O rulebook from 1969
4 http://www.nycsubway.org/index.html, the link to the signal section is: http://www.nycsubway.org/tech/signals/.
5 http://www.railroadsignals.us/nycentral.htm - New York Central rulebook from 1937.
6 http://www.railroadsignals.us/co1.htm - C&O/B&O rulebook from 1969.
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NEW 05/07/2007
Last Modified:
12/30/2009
