Signal Question and rule term

NW Mailing List nw-mailing-list at
Thu Oct 31 11:26:48 EDT 2013

Grant Carpenter wrote:


I have never understood why "medium" came about for aspect names on the
N&W. It sounded big-time? The term has little relevance to how the
diverging aspects were applied in the field.

I agree 100%, Grant ! The matter could not be stated more succinctly.

I suspect that the word "Medium" came into the N&W vocabulary due to a suggestion of the Train Rules Committee of the American Railroad Association back in the 1920s. That suggestion was that the "indication" for the Approach Signal be worded thusly: "Proceed preparing to stop at next signal. Trains exceeding Medium Speed must at once reduce to that speed." (Various railroads massaged the exact wording around, but the meaning was always the same.) "Medium Speed" was defined as "One half the maximum authorized speed, not exceeding 30 MPH."

The 1930 Rule Book does NOT use the term "Medium Speed." The indication of the Approach signal is simply, "Proceed prepared to stop at next signal."

The 1945 Rule Book DOES use the term "Medium Speed." The indication of the Approach signal has been revised to read, "Prepare to stop at next signal. Trains exceeding Medium Speed must at once reduce to that speed." BUT the 1945 book does not associate the term "Medium Speed" with any of the other signal aspects. And in the 1945 book there appears, for the first time, a definition of Medium Speed in the definitions section: "One-half the maximum authorized speed, but not to exceed 30 miles per hour."

The 1951 Rule Book carries, for the first time, signal aspects called Approach Medium, Medium Clear and Medium Approach. But the speed requirements for these three new aspects is not "at Medium Speed"... it is "at prescribed speed" (which means, Look up the speed in your Time Table Special Instructions!)

So, the whole conception of signaling and its application was in flux, evolving. The fast and complex railroads, like the NYC, were at the vanguard in implementing the new signaling concepts because the savings of moving trains faster meant big bucks to them... if you move your trains faster, you might not have to build additional tracks. The new concepts and methods filtered down to the smaller and slower roads a couple of decades later.

There were also other things which were in flux in the 1920s and 1930s, things which we now take for granted and never realize that they had a developmental history. Two of them are:

(1) "Slow Speed" (the 15 MPH speed tow given over switches having #10 frogs) did not come into the signaling vocabulary until around 1915. Frank Patenall, the brilliant Chief Signal Engineer of the B&O, in 1914 published an article called "The Slow Speed Signal" in which he wrestles with and gives perhaps the first good formulation of how to signal over #10 frogs, and how to give "calling on" indications.

(2) And the concept we today call "Restricted Speed" had a long and very tortured development. About ten years ago, a fellow at the FRA's Washington office wrote a brief research paper which sought to work out the origins and many permutations of the "Restricted Speed" concept over the years. The N&W at first used the term "at low, restricted speed," and later adopted the term "Restricted Speed" from the Standard Code of Operating Rules and gave it a formal definition. But even that definition changed over the years...

I am really surprised that anyone else caries about all this essoterica. It is, you know, the province of curmudgeons and dilettantes.

-- abram burnett,
retired turnip farmer
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