FOR those with a need for speed, it will take the thrill out of driving, but the government believes an in-car “spy” device could save lives and make speed cameras and road humps redundant.

The device, which automatically applies the brakes or blocks the accelerator to prevent a driver from exceeding the speed limit, has been successfully tested on Britain’s roads for the first time.

The trial in Leeds was part of a two-year study into “Intelligent Speed Adaptation” (ISA) commissioned by the Department for Transport, which wants to reduce road casualties by 40% by 2010.

Transport for London (TfL), Ken Livingstone’s transport agency, is also interested in the technology and has asked researchers at Leeds University — who conducted the DfT trial — to produce a feasibility study for the capital.

TfL is considering initially fitting limiters onto public service vehicles, such as buses and taxis. However, it also wants to encourage private motorists to install the devices and could give a discount on the congestion charge, which tomorrow rises from £5 to £8 a day.

Experts believe the system — which monitors the speed limit via satellite tracking — would cost up to £1,300 to install now but is likely to be fitted as standard in most cars within a decade.

For the initial trial in Leeds — the first of four six-month trials — researchers recruited 20 volunteers to drive specially modified Skoda Fabias.

Each car was fitted with a black box containing a digital road map showing the speed limits on every road in the city.

A satellite positioning system told the car where it was on the map and alerted the driver, via a digital display on the dashboard, each time he entered a zone with a new speed limit.

If the driver attempted to exceed the limit, a signal was sent to the accelerator or brake pedal to intervene.

“If the driver is demanding something greater than the speed limit, that demand is ignored,” said Oliver Carsten, the research leader and professor of transport safety at Leeds University. “In a 30mph zone the car will basically not accelerate above 30mph.”

Tests following the trial revealed that volunteers were also less likely to break the speed limit when the system was switched off.

Previous modelling has suggested that if limiters were fitted to all cars in Britain, the number of people injured on the roads each year would fall by 20%, while fatalities would be cut by 37% from their present level of 3,221.

Jeremy Clarkson, co- presenter of the BBC’s Top Gear programme and a Sunday Times writer, disagreed. “If you put speed limiters on cars so that they can only go to a certain limit you end up with terrible bunching which actually causes more accidents,” he said. “Tony Blair is not going to tell me how fast to go.”

Car manufacturers are also sceptical about the benefits and would be likely to resist any attempt by the government to make limiters compulsory.

A DfT spokesman said it had no plans to make the use of speed limiters mandatory. “It will be for the industry to take forward the technology in response to consumer demand.”