COLOURED LIGHT

Evening Post, Volume CXXVII, Issue 59, 11 March 1939, Page 28

COLOURED LIGHT

REDUCTION OF POWER

THE SCIENTIFIC ATTITUDE

Thousands of motorists use headlights giving a coloured light in the belief that they possess advantages over white light of the same power for driving at night or in fog. It is claimed that with coloured light, objects on the road are more easily seen, that glare is reduced, and that the coloured, rays penetrate further into mist or fog.

Legislation in France compelling the use of headlights emitting yellow light has served to focus attention on this problem, investigation of which was undertaken by the British Medical Association. The association reported that extravagant claims had been made for yellow headlights, and that no definite recommendations could be made in any direction.

It is • emphasised that, in deciding upon the relative merits of white.light and coloured light, it is of great importance to note that when coloured glass is put in front of a lamp it not only colours the. light, but also reduces its brightness. According to the "Scientific American," false conclusions are often drawn through failure to separate the effects of change of colour from reduction of brightness.

None of the claims made in favour of using a coloured headlight beam, yellow in particular, rather than a white beam of the same power, has been substantiated. The claim for a greater range of visibility in fog may be regarded as definitely disproved. As for the other claims of less glare and greater facility of vision, the evidence is inconclusive, but it is apparent from the information at present available that no considerable advantage can be secured by using coloured light.

A feature in a new State car ordered