NW Mailing List nw-mailing-list at
Fri Aug 16 09:30:36 EDT 2013

I checked the signal aspects on the web page for N&W aspects against
the operating rules and aspects issued on November 18th, 1951, and
they are pretty much the same aspects. So, for the aspects used at
the end of the steam era, those will cover the basics.

As for a "standard" set of color position signal aspects, I know of
none. Each railroad had their own set of rules, and the N&W tweaked
their aspects. They first began showing up in N&W's 1930 rules, and
pretty much mimicked semaphores. Later, after semaphores disappeared,
they did away with the second, and even third horizontal aspects.

(Do not confuse semaphores with the train order signals used at
stations, etc. While they technically could be called lower quadrant
semaphores, they were used to issue train orders. If the blade was
hanging down, they knew there were no orders for them.)

Now, back in that time period, all signals in CTC territory were
numbered. The automatic (or intermediate) signals between control
points were numbered by milepost location generally speaking. The
interlocking numbers corresponded with the number on the CTC machine
the dispatcher used to operate the signals. For the end of steam,
that interlocking number plate should have a letter S centered under
the number portion of the plate.

If I get a chance this weekend, I will work up an aspect chart based
on the rules that I have in hand from that era.

Ben Blevins
Lead Signalman

On 8/15/13, NW Mailing List <nw-mailing-list at> wrote:

> Lynn,

> Go here for a PRR rule book and signals:


> Scroll down to Operations and Management, then click on PRR Rule book 1925.

> The previous N&W link that I posted will suffice for the N&W signals.


> Jimmy Lisle


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