Everlasting bulb lightens the load

A CONUNDRUM that has long plagued governments and companies alike - how many people does it take to change a light bulb? - could soon be consigned to history's out-tray.

Scientists have developed a light bulb made from a new material called gallium nitride that lasts 100 times longer than those now in use. It shouldmake regular bulb replacements unnecessary.

The everlasting light bulb is being tried out at two sets of traffic lights - on the M32 near Bristol and in Marsham Street, central London' - to see if it is suitable for the millions of red, amber and green lights.

Existing traffic light bulbs, which have a longer life than the domestic variety, are replaced every six months by teams of electricians working in the small hours when few vehicles are on the roads.

The new bulbs last for at least 10 years and consume only 20 per cent of the power of the conventional tungsten-halogen traffic lights, said Colin Humphreys, professor of materials science at Cambridge University.

"I'm told the energy consumption of traffic lights in this country is two medium-sized power stations. It sounds hard to imagine until you realise that at every junction there are at least eight lights on all the time," he said.

The Cambridge research group has received an pounds 800,000 government grant to develop gallium nitride technology.