RECOMMENDATION OF THE AMERICAN ASSOCIATION OF STATE HIGHWAY OFFICIALS REGARDING PRECAUTIONAL AND DIRECTIONAL SIGNS.
It is recommended that this Association go on record as approving the following:
A. For luminous signs or signals-
(1) Red to indicate danger or stop.
(2) Yellow to indicate caution or slow.
(3) Green to indicate go.
B. For non-luminous signs -
In view of the fact that the effectiveness of non-luminous signs depends upon visibility at night under automobile headlights, we recommend the use of a light background, preferably lemon yellow, with black lettering as a color scheme for these signs. The present knowledge of other color combinations does not justify a further recommendation at this time.
C. Shapes of non-lumious signs -
(1) Railroad warning sign Round
(2) Danger or Stop sign Octagonal
(3) Caution or Slow sign Diamond Shape
(4) Look or Attention sign Square
(5) Road markers Some characteristic or conventional shape different from the above.
(6) Directional and Infor- Rectangular
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