Object lesson No. 15

14th April 2000 at 01:00
Tyger! Tyger! Burning bright, in the forests of the night. The glint in the eye of a cat inspired William Blake to verse long before Percy Shaw saw the same thing on his way home one night and had an illuminating idea.

Driving down the poorly lit roads around his home in Halifax, Mr Shaw had got used to seeing his way by following the gleaming tramlines lit up by his car's headlights. But trams were disappearing from the roads, and their lines were being pulled up. As Mr Shaw mused on the road safety implications of this, his eyes met those of a cat reflected in his headlights. The solution was staring him in the face. Cats' eyes - and those of dogs, rabbits and deer - reflect light from a mirror-like layer at the back of the retina called the tapetum. This concentrates low levels of light and explains their superior night vision.

Percy Shaw's invention copied nature's design right down to the eyelid: every time a car runs over a catseye, the rubber casing slides over the lens, cleaning it in the blink of a eye. Mr Shaw, who had left school at 13, patented his design for catseyes in 1934 at the age of 23.

Jim Callaghan, who introduced them when he was roads minister in 1947, later said they were the one of the most useful things he had done for the country. Catseyes made Mr Shaw a wealthy man, but he preferred not to bask in their reflected glory. His only luxury was a Rolls-Royce, and he lived in the same house he had been brought up in until his death in 1976.

His brilliant invention has become a middle-of-the-road fixture - there are around 400 dotted along every mile of Britain's 6,500 miles of motorways and trunk roads, and the factory in Halifax that produces them turns out a million every year. However, they could soon be overtaken by the less romantically named intelligent road stud - a solar-powered version which emits different-coloured lights warning drivers of hazards.

But Mr Shaw's invention, which has shown the way for 65 years, will remain a shining example of British ingenuity.

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