The digital speed map of Britain is an essential first step towards introducing Intelligent Speed Adaptation, known as ISA, which automatically applies the brakes or blocks acceleration.

An on-board computer linked to a satellite positioning system will use the digital map to identify the local speed limit. If drivers attempt to exceed the limit, they hear a series of bleeps and the accelerator pedal starts vibrating.

The device will be offered initially as an optional extra by car manufacturers but ministers have not ruled out eventually making some version of the system compulsory.

The Government’s senior transport adviser believes ISA could eliminate the need for speed cameras and road humps once the majority of vehicles have been fitted.

David Begg, chairman of the Commission for Integrated Transport, said: “Motorists will choose to have this technology on their cars because it will prevent them from inadvertently exceeding the speed limit and will save many from losing their licences.

“Speed cameras and road humps could be removed because there would be far greater compliance with the speed limit.” Professor Begg said that courts could be given the option of ordering motorists to have ISA fitted to their cars as an alternative to a driving ban.

The Department for Transport has commissioned a series of trials of ISA in Leeds and Leicester. But there is no central speed limits database for the whole country and many local authorities have poor records of the limits on their roads.

The Department for Transport believes the absence of a national database is hampering development of ISA, which it hopes will initially be offered as an option by car manufacturers.

The DfT has now invited expressions of interest from the private sector to create a national speed limits database.

A DfT spokesman said: “If the whole country was mapped, it might make it more logical and practical for manufacturers to consider offering ISA. There could well be road safety benefits from ISA.”

Oliver Carsten, Professor of Transport Safety at Leeds University, said: “The digital speed map is a necessary first step for a commercial ISA system, which would prevent many road deaths and injuries.”

A previous research project by Professor Carsten estimated that ISA would reduce crashes involving deaths or injuries by 20 per cent. But he said that the casualty reduction would double if a more advanced system was introduced which took account of conditions.

He said that even the simplest versions of ISA would prevent drivers from drifting over the limit and being flashed by speed cameras. “Roads are complicated and people make genuine errors when guessing the limit. Not everyone can measure the distance between lamp posts and ISA will remove uncertainty by displaying the limit on the dashboard.”

The Automobile Association said that drivers would welcome ISA as an extra tool to help them to drive safely but did not want “Big Brother” in the back seat taking control of the car.

Paul Watters, the AA’s head of roads policy, said: “There are concerns that this system could be draconian and restrict freedom. But as long as it remains optional and can be switched off then it could be very useful.”

Several other European countries, including Norway and the Netherlands, have already produced national digital speed maps or are about to complete them.

Initial results from the trials suggest that people might feel frustrated by the system if only a minority of cars have it. But once most vehicles are constrained, drivers are inclined to welcome it.

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