Why we use red, green &yellow for traffic signals?

      Why we use red, green &yellow for traffic signals?

PROF WAQAR HUSSAIN

         Science says that red colour has long wavelength, and is visible from longer distances than the other two. But the use of these colours in traffic signals has different reasons. 

                  Basically the colors came from the British railway semaphore signals that used red (danger) in the lanterns to warn of danger ahead. Green was originally white to indicate “all is clear". However, railway department later found out that a broken red lens in a signal could give a false ‘clear indication’ and could lead to many disastrous incidents. Green then was chosen because of avoiding false indication and further, it has cooler contrast to the other colors.

            Yellow signal was introduced by America as a cautionary indication in two light signals by combining the red and green lamps. Because from a distance; the 

mixture of red and green colours produced yellow for some persons. And for those persons, it was ‘all clear’ sign. 

                       There is psychological basis for these colours also! Different colours evoke different emotions in humans. Red generally symbolizes threat, danger or warning, making it a good choice for "stop." Green is calming and soothing because it is prolific in nature and is a sign of health and abundance, so it might have lent itself to mean "go." While yellow is associated with warmth, happiness. Despite these connotations, it was chosen to symbolize "caution." Perhaps, it contrasts well with green and red, and is highly visible without being too harsh and nasty on the eyes of the motorists. Today, yellow is almost transformed as a warning symbol for both traffic signs and alert systems.