L/R Number Plates on N&W Home Signals, And Other Matters

NW Mailing List nw-mailing-list at nwhs.org
Sun Jun 24 23:08:12 EDT 2012

Someone recently wrote me inquiring about the N&W's practice in putting number plates on its Position Light home signals.  (Most railroads plated only the automatic block signals, and the absence of a number plate served as a reminder that a signal without one was a home signal.)  My response to the query trails.  Not wishing to start any fights or be inflamatory, and hoping that my humble musings may be heuristic in some way for others who think about such historical matters ...


-- abram burnett.



Jim et al:


The N&W did several inscrutable things with its PL signals. Things that seem strange to us, working with the full PRR PL signal system.


As background, one must understand that the N&W, beginning with its first PL automatic block signals about 1928 on the Shenandoah Division, and then continuing with its full CTC PL systems of the 1940s, chose NOT to adopt en bloc the entire system of PL signaling that the PRR, US&S and Corning Glass Works had perfected. RATHER, the N&W chose to have its PL signals simply replicate the position of the old semaphore arms. In some cases, this resulted in THREE full arms/backgrounds on some signals, with an ADDITIONAL single marker light at the bottom (indicating that it was a home signal... a very old usage in the signal business.) This accounts for the monstrously high PL signal masts that survived on the N&W right up until the end. That old bottom single "marker light" apparently survived as the "stop and stay" marker in later N&W practice.


Nor did the N&W fully commit to the PRR's speed signaling system. The 1945 N&W Rule Book does associate "Medium Speed" and "Slow Speed" with some of the aspects, but later even that was dropped, and the signals became simply route signals giving only "diverging" indications (and the engineman had to use his Time Table to figure out the speed allowed over any given switch by a "diverging" aspect.) What an absolute waste of a good signal system... especially since someone else had already paid for all the R&D work.


Another anomally in the N&W signal system is the placing of signal number plates on home signals (with L or R prefixes, for Left or Right.)  These numbers, of course, correspond to the numbers of the controlling levers, with L or R indicating Left or Right position of the lever (and movement of the trains) as the signalman faced the machine.


Yet another anomally is that the N&W PL dwarf signals did not display a Slow Approach indication. Rather, what we would call the Slow Approach aspect was, for the N&W, a Restricting. Another waste, since all four lamp housings were already on the PL dwarf signals and it would have taken only one more relay to give the Slow Approach. I think this also shows the "semaphore mentality" that probably prevailed in the N&W Signal Department at the time they were installing their system.


Nor did N&W adopt the very "transparent" relay and wiring nomenclature system standardized by the PRR, and N&W prints for signal system wiring are rather unfriendly, in my opinion.


So it appears that the N&W people designed their own signal system and simply chose the PL's for their field hardware, being tied to an older "semaphore mentality" without a lot of reference to what was going on elsewhere in the world of signaling.  (On the other hand, the N&W was very quick to adopt US&S's Coded Track Circuits very shortly after they were invented.)


But, in all fairness, it must be said that the N&W did not face the same problems as the PRR with its 4-track system, much higher speeds, massive terminals, truly huge interlockings, and trains following each other on close headways.


I wish I could have talked with some old timer who worked in the N&W System Signal Office and was around during the 1930s and early 1940s, but I never met such a man. Hopefully the N&W Historical Society archive at Shaffers Crossing, West Roanoke, will some day discover a huge box of Signal Department materials with all kinds or correspondence from the 1920s, 1930s and 1940s. Without that kind of documentation, we're just kinda guessing about why they did what they did.


BTW, I'd be pleased to have my email addy placed on any signal distribution lists of your friend Dick and his confreres.
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