Date for Change in Signal Colors?

nw-mailing-list at nw-mailing-list at
Thu Jul 14 23:53:07 EDT 2005


Radford Division TT's show that the change was made at the same time. The change first appears in the No. 8 TT (USRA) dated Dec. 8, 1918.

Jeff Sanders
----- Original Message -----
From: nw-mailing-list at
To: NW Mailing List
Sent: Tuesday, July 05, 2005 2:22 PM
Subject: Re: Date for Change in Signal Colors?


The following quotes from American Railway Signaling Principles and Practices, Chapt. 1, "History and Development of Railway Signaling," Signal Section, AAR, 1953, outline the evolution of signal colors for the industry:
In a paper delivered in 1899, "The usual colors for railroad signals almost universally adopted in all civilized counties are: white for safety, red for danger, and green for caution. These colors were agreed upon at a congress of railway men held in Birmingham, England in 1841."

In 1894 the pertinent ARA [American Railway Association - predecessor of the AAR] committee "...recommended continuing the use of green for caution and white for safety. The ARA then voted to continue the use of white for safety."

"It was obvious in this period (the late 1890's) that with each railroad selecting its own combination of different shades of colors ... no uniformity of hue or saturation existed. Reds varied from orange to a very dark red; greens ranged all the way from a yellow chrome to blue.... As for the yellow for a third night indication, difficulty was experienced in that the tints ranged from a reddish-yellow, which was easily confused with red, to a greenish yellow which was easily mistaken for green."

"In 1904, Dr. Churchill was employed by the Corning Glass Works to establish an optical laboratory for special research on colors and the optics of signal glassware. A period of great activity was witnessed in the new Corning optical laboratory from 1905 to 1908"

In 1908, a specification for signal glass was approved by the RSA (Railway Signal Association). "As a result the railroads gradually abandoned their individual color requirements to use glasses meeting the RSA specifications, and by 1910 the use of white for 'clear' was quite generally abandoned when red for 'danger,' yellow for 'caution' and green for 'clear' were adopted."

Research continued, and in 1931 glasses suitable for standards were produced. "One set was given to the Bureau of Standards for file in Washington, DC; a second set was held by the Signal Section and a third set was kept on file at the Corning Glass Works." There were subsequent revisions to the specification.

Available documents in the NWHS archives indicate the change occurred later on the N&W. Op. Rule Book eff. April 1, 1917, Rule 10 Color Signals still prescribes red for STOP, green for PROCEED WITH CAUTION, and white for PROCEED. This was changed in the next available Op. Rule Book eff. Nov. 16, 1930, Rule 10 Color Signals which prescribed red for STOP, yellow for PROCEED AT RESTRICTED SPEED, and green for PROCEED. So, the change occurred sometime between those dates, but to pin it down closer, the Norfolk Division employee TT's were examined. TT No. 7, eff. Nov. 3, 1918 made no mention of any change in signal colors, but in TT No. 8, eff. Dec. 8, 1918, Rule 19 modifies the pertinent rules in the Book of Rules to change GREEN to YELLOW and WHITE to GREEN.

At the time of the change, the railroads were under the control of the United States Railroad Admininstration, so it is likely that it was the USRA that required the N&W to change in the interest of standardization.

Time was not available to check other division TT's to see if the other divisions changed signal colors at the same time as the Norfolk Division.

Gordon Hamilton

----- Original Message -----
From: nw-mailing-list at
To: nw-mailing-list at
Sent: Saturday, June 25, 2005 9:24 PM
Subject: Date for Change in Signal Colors?

Has anyone figured out from the literature the date that the N&W made the switch from

WHITE for "clear"
GREEN for "approach" or "permissive"
RED for "stop


GREEN for "clear"
YELLOW for "approach" or "permissive"
RED for "stop" ?

The ICC investigation report covering the rear end collision at Belspring on July 16, 1915, seems to indicate that the change had not yet been made, as the operator at Pepper wrote "Block Clear" on the Clearance Card when he should have written "Block Green" (i.e. "permissive") to advance Ex 1425 West into an occupied block.

I think I recall that it was only about 1912 that Corning Glass Co. figured out how to make yellow glass that was suitable for railroad signaling purposes (i.e. chromatically distinct from any shade of red, and having adequate "transmissibility".)

The answer surely lies in the timetables at the Archives. Git busy, Harry B. and James B. !!!!

-- abram burnett,
writing from the La-La Land of senile old fuddyduddies


NW-Mailing-List at
To change your subscription go to


NW-Mailing-List at
To change your subscription go to
-------------- next part --------------
An HTML attachment was scrubbed...

More information about the NW-Mailing-List mailing list