In the year 1922, the American Association of Highway Officials (AASHO) decided to standardize the STOP sign owing to its increased use then. Before this, the sign was printed on a white metal sheet with black letters. The association’s motive was to bring uniformity to its shape and color. In 1923, the Mississippi Valley Association of State Highway Departments gave the STOP sign its iconic shape – an octagon and in 1924, the AASHO advised the use of yellow for all danger and caution signs including the STOP sign.
The STOP sign now had eight sides with the word STOP written with black on a yellow background. While the use of yellow stayed consistent until 1954, the color of the text on the yellow sign saw further changes. In 1935, traffic engineers formed the 166 page long Manual on Uniform Traffic Control Devices that advised the use of red or black letters on a yellow background for STOP signs.
Why Was it Yellow?
The STOP sign from 1924 to 1954 was yellow because it couldn’t be red. According to the MUTCD, the report prepared by the AASHO in 1924 acknowledged the superior visibility of yellow and advocated its use in the sign. It rejected the use of red because it did not provide adequate visibility at night. Moreover, limitations in technology to produce a reflective material in red that was durable enough to last prevented the use of this color in the STOP sign. “Red has always been associated with stop” “The problem was they could not produce a reflective material in red that would last. It just was not durable until companies came up with a product in the late ’40s, early ’50s.”- says Professor Gene Hawkins, expert on the history of the STOP sign. [Source: The New York Times]
When Did the Sun Set on the Bright Yellow STOP Sign?
In 1954, when the MUTCD was revised, the use of white letters on a red background for the STOP sign was advocated. The change in the color was proposed to align it with the color coding system developed for the railroad and traffic signals. The change in color of the sign turned many yellow STOP signs obsolete. The rusty old yellow signs now find their place in road signs collectors’ treasure retelling the tales of a golden past.