A large number of men are color blindabout one out of every 25.
Considering the enormous increase in automobile traffic, the safety of which at night depends largely on being able to distinguish red and green, the very colors these men confuse, this constitutes a distinct hazard.
It is suggested that the primary requisite for a driver’s license be a test for color blindness.
It would probably not be necessary to prohibit such men from driving cars. I know one physician who is color blind and who has driven a car many years without an accident. But he knows of his color blindness and is doubly careful. Most color blind individuals do not realize their own deficiency. When the fact is brought to their attention they are frequently able to make allowances or arrange to have a companion at night so that they are as safe as normal visioned drivers. There are, so far as I know, no data as to the percentage of color blind drivers involved in automobile accidents.
It is unfortunately impractical to substitute any other colors for red and green signal lights. White, yellow or orange lights are so common that they have no significance. Blue lights do not penetrate far enough. Red and green are definite, primary colors, are readily distinguished a long way off, are not changed or confused by smoke, fog, steam or other atmospheric changes. Besides, they have now a definite and deeply-set psychological association in the public mind.
It took several years in the early days of agitation to convince railway executives that tests for color blindness were necessary for their employees. Cures were attempted in order to evade the issue. But experience has proved that there is no way to cure congenital color blindness or even to alleviate the defect.