Colour-Blindness and Traffic Signals

Abstract

The danger from colour-blindness may be greatly minimized by a careful selection of the colours used in traffic signals. With the exception of the rare class of the totally colour-blind, all the partially colour-blind recognize some colours with ease and certainty. The colours recognized are different with each class of the colour-blind. A certain variety may fail with one test, but a man who is much more colour-blind may pass it. A man may fail to distinguish a certain red light, but distinguish with ease another, red light which looks exactly the same to the normal-sighted. Another variety may distinguish with ease a green light, but fail to recognize another green light which appears very similar to the normal-sighted. The old terms "red blindness," "green blindness," and "red-green blindness" are quite erroneous, and should be discarded, as stated by a committee of the British Association. As is well known, 50 percent of the dangerously colour-blind pass the Wool test. A similar result is found with other tests which are not constructed to detect all varieties of colour-blindness. I have often given a demonstration when I have shown that the candidate will fail with a number of tests and pass completely with several others. A colour-blind person does not guess unless he is in obvious difficulty, and this is at once apparent. Unlike at sea, the motorist is helped by the position of the lights, as he can note the order in which they come on or go off, and his distance from them is comparatively short. Language: en