Cars should be fitted with devices to regulate their speed to cut fatal accidents by a quarter, a British government advisory body said today.

The Commission for Integrated Transport and the Motorists' Forum said the voluntary use of so-called intelligent speed adaption would cut 40,000 road deaths over a 60-year period.

The proposed system would automatically slow the engine and apply the brakes to keep a car within local speed limits, although the driver would be able to override the limiter.

It said the limiters would also reduce carbon dioxide emissions by 6 percent on roads where cars go at speeds of up to 70 miles per hour.

The commission called on the Department of Transport to start building a database of road speed limit maps which would be needed to operate the system.

It said was not recommending mandatory limiters which allowed no override, although it estimated these would have the greatest effect by reducing fatal accidents by 44 percent.

A Leeds University study for the commission calculated the potential reduction in accidents by analysing the results of a government-funded study in which 79 drivers used cars fitted with a speed limiter for their everyday motoring.

The Motorists' Forum, which is part of the commission and represents car users' views, said it backed the study.

"The UK has an enviable record on road safety but we still kill nearly 3,000 people on our roads each year," said the forum's chairman, Trevor Chinn.

But motoring pressure group Safe Speed said limiters could make driving more dangerous by taking responsibility away from drivers.

Safe Speed spokeswoman Claire Armstrong said truck drivers in speed-limited lorries go into "zombie mode".

"They stick foot on floor because they know the equipment will not go any faster," she told BBC radio. "They stop paying attention to the road. That makes it highly dangerous."

The Department of Transport said it had no plans to enforce the use of speed limiters but said they could help road safety for drivers who wished to adopt them.

"We will work with vehicle manufacturers, local authorities, insurance companies and others to consider what steps should be taken to support the future availability of the technology," said a department spokesman.