Last N&W CPL Signals in Tidewater Coming Down - Height of Masts

NW Mailing List nw-mailing-list at
Wed Jul 6 17:49:30 EDT 2011

Miceal asked, concerning the height of N&W Signal Masts:

>> Does anyone know why the signals are at such a height? <<

Very few people have asked this question, but the explanation is s imple. Most N&W Position Light Signals are on masts which were erected to hold semaphores. In semaphore days, what kind of engines did you have? Steam engines, of course. And therein lies part of the explanation.

1.) The "day indication" of a semaphore was given by its arm (blade.) If the arm could be put in a position above the horizon, where the background of visibility was the sky, rather than foliage or a mountain , the engineman could more easily distinguish the position of the semaphore arm.

2.) Putting the semaphores up high also lifted them up, as much as possible, above the steam and smoke that were often present around an engine and which, in certain wind conditions, "rolled down" (i.e. was blown down) over the side of the engine. I believe there was a significant wreck of N&W No. 26 in the early 1950s, caused by the engineman missing signals due to smoke "rolling down" over the side of the engine and obscuring his view.

The N&W and the PRR mounted their signals higher than other roads, from my observation, as well as some of the New England roads. Of course, in three and four track territory signal bridges or cantilevers had to be be used, and that in itself raised the height of the signals materially. In double track territory, "bracket masts" (such as used by the N&W) sufficed.

I have never seen reference to these problems and practices in any signal engineering literature of the railroads during my career. Indeed, the problem was probably moot by about 1950 in the railroad industry. If any of the older (1910-1940) N&W Signal Department Standard Plans still survive, perhaps someone could check them to see if this problem was addressed formally.

And you are also correct in your observation that in today's world (where we longer have to deal with engine smoke and the position of a semaphore arm) the tendency is to place the signal so that it is near the engineman's line of sight. In color light signal territory, I believe the engineering recommendation for a "ground mast" Color Light signal was to place the red lamp/lens as close as possible to the engineman's eye level, as this was the one most critical to safe operation.

You are perceptive, Miceal, to have asked a question like this ! Keep up the good work.

-- abram burnett
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