Academics in California argue that if many drivers view the maximum speed as unrealistically low they will habitually break it, causing "traffic turbulence" in their wake.
In Britain, drivers regularly exceed the maximum speed. According to the Department of Environment, Transport and the Regions, nearly 57 per cent of motorists break the 70 mph limit. Motoring organisations say this shows the need for the Government to review the speed limit.
"We would prefer that the speed limit was set at the more appropriate level of 80 mph. People are very rarely stopped by the police for travelling 10mph over the current limit. If it were raised, then it could and should be enforced," said Edmund King of the RAC.
With some motorists prepared to travel at 90mph while others motor at a more sedately 50mph, the US researchers say drivers find themselves having to brake suddenly when they meet slower vehicles.
"If you set a limit at a level that drivers do not agree with, some will disagree and violate it, others will obey it. Either way, you get speed variance - and that causes accidents," said Charles Lave, a professor at the University of California.
Prof Lave believes that raising speed limits reduces turbulence in the traffic stream. "In November 1995, the US Congress gave states permission to raise speed limits from 55mph. This saw some states - such as Montana - even dispense with speed limits. And fatalities fell by 0.7 per cent in 12 months."
Some areas have seen spectacular results. Colorado, which raised its limit to 75mph in May 1996, saw speed-related deaths drop 8 per cent in a year.
In Britain, motorways are the safest places to drive. Government statistics show drivers are eight times less likely to have an accident on a motorway than a road in a built-up area.
Since 1990, the police have taken a hard line against raising the speed limit. But some senior officers have broken with the consensus. In 1995, Paul Whitehouse, chief constable of Sussex, earned the wrath of his peers when he claimed 70mph was too low and called for it to be increased to at least 80mph.
Safety groups oppose any increase in speed limits. "If you put it up to 80 mph, it won't be long before there are calls for people to drive at 90 mph," said Roger Vincent, a spokesman for the Royal Society for the Prevention of Accidents.Reuse content