RAILROAD SIGNALS of the U.S.

COLOR POSITION LIGHT SIGNALS

CPL, or Color Position Light signals were exclusive to the Baltimore and Ohio Railroad, and it's affiliates.  You could find them anywhere the B&O went.   However, now that all of the former B&O lines are part of CSX, they have been accelerating their efforts to replace the CPL's with modern 3 color light signals everywhere (yuk).

Other railroads using CPL's are the Staten Island Rapid Transit (SIRT)(now part of the MTA), the former B&O Chicago Terminal, and the former Alton and Southern.  Dwarf CPL's were also chosen to be used in and out of Union Station in Washington DC, altho they appeared on signal and cantilever bridges above the tracks.

CPL dwarf signals also enjoy being the only dwarfs which, if so outfitted, can display ALL of the aspects of a high signal.  The only one I ever saw so configured was at the B&O Railroad Museum in Baltimore.  However, I don't know if the signal before it came to the museum was originally in this form, or if it was put together just for display.  Since the snow cave-in of 2003, the signal has not been on display because the museum has decided not to use the outside wall for displaying much of anything.

Check out Michael's primer for more info on CPL's.

   Michael Watnoski's primer on CPL signals 

The Signal

The main CPL signal "head" consists of a number of individual lamp assemblies mounted to a circular background 3ft-4" in diameter.  The background is mounted to the mast with two heavy duty steel straps and U-bolts.  Mounted to the backside of the background is a junction box, where the cables from the relay cabinet terminate, and individual wires go out to the lamp assemblies.  A fully populated CPL head would contain eight (8) lamp assemblies, two lamps for each aspect.  As with the Pennsy Position Light signals, the B&O Color Position Light signals were an attempt by the designer to simulate the position capability of the semaphore signal.  On some older installations, the transformers (one was needed for each circuit that had to be illuminated) to step down the 120VAC were installed in the junction box, but because of the "high-voltage" in there mixed with low voltage, and the safety hazard it presented, I guess they eventually decided to remove them... cost to provide a separate transformer for each circuit may have also been a factor.

A CPL signal also had what are known as marker lamps located above and below the main signal head.  Very few CPL signals consisted just of a main signal head, most had at least one marker lamp.  If it was a high signal, the sole white marker lamp was usually directly above, so the signal could display a clear aspect.  Without the marker lamp, the green indication was slow-approach slow.  A CPL signal could contain as many as six (6) marker lamps, and the only one we are familiar with used to be in Deschler OH, but has been replaced with color light signals by CSX.  An almost full CPL signal still exists in Baltimore, the aspect missing is restricting on the main head.

  Pages from a 1935 US&S catalog dealing with CPL's

  A single aspect/restrict only CPL adjacent to the Westport Light Rail station in south Baltimore

 The 3 signals below and Bailey's Wye are shown on this B&O map of the central Baltimore MD area

  An almost full CPL, has all 6 markers, only missing the restrict aspect 
Located in south Baltimore along the mainline to DC at "Carrolls" - can be seen from NB I95  082805

   A 3 CPL signal bridge - located just south of Baileys Wye in south Baltimore  082805 

   COMING - A CPL signal with 5 markers - for NB reverse traffic on the main line to DC in south Baltimore  082805

  Two aspect CPL by Washington Blvd and Monroe St, in south Baltimore 031106

  Map of the Bailey's Wye area

   CPL on the SW leg of Bailey's Wye in dntn Baltimore, for freights coming out of Riverside Yard.

     A couple of shots of signals on the south side of the Harpers Ferry tunnel

 

  OTHER PICTURES
 

CPL's a plenty at the west (south) end of Mt. Winans yard in south Baltimore MD, with an approaching westbound CSX freight, taken around 1995.  These signals are still there, altho for who knows how long, as just a little ways down the tracks, they replaced CPL's around the curve in Landsdowne.  The freight is getting ready to cross Gable Ave, a fairly good photo spot off of Washington Blvd, near Patapsco (I wouldn't venture into the yard, tho).  This freight might have come from Curtiss Bay if it took the crossover just off the right side of the pix, if not, it took the long way around coming from Baltimore going thru Mt. Clare yard A.  For a B&O map of the area, click HERE.  The map is dated 1988, but does not have the signal bridge by Ridgely St on it.  Curious.  There is a little arrow on the map along Patapsco Ave that shows where the picture was taken from.  The map covers from Lansdowne Rd on the south side to Camden Station (before it's current 2 track configuration). 

The above picture was taken from Gable Avenue, looking in the direction of my vantage point in the photo above this one.  At the bottom, you can see a CPL dwarf.  At the top of the photo, and the two bright dots in the middle, are high CPL's.  The two large white dots are streetlamps on the bridge that I took the other photo from, and finally, the cluster of three lights is a freight waiting to go into Curtis Bay, sitting under the bridge.

New 10-6-2006
Last Modified: 27-Nov-2008