NEW digital speed cameras which can trap three motorists per second are to be introduced on the North West motorway network.
It follows a successful trial in roadwork areas of the M6 in Cheshire when more than 200 speeding motorists were snared over a six-week period.
The Highways Agency intends to use the new cameras to enforce temporary speed limits through roadworks on the region's motorways.
Known as the Specs system, the digital cameras do not require film and are always switched on. They operate in pairs, with one installed at each end of the roadworks.
Both cameras record the speed of a vehicle as it passes by and then an average speed is calculated.
The Highways Agency is hailing the Specs system as the way forward in speed checking technology.
A spokesman said: "Following the success of the trial in Cheshire, there are plans to use the new cameras on stretches of motorway where there are substantial roadworks, wherever possible.
"The speed recorded by these cameras gives a more accurate picture than that registered by a conventional speed camera, which only records speed at one point.
"The problem with this is motorists get to know where an individual camera is and slow down as they pass it, then speed up again.
"The new cameras force motorists to keep to the speed limit for a considerable distance." But the Institute-of Advanced Motorists says the increased presence of speed cameras means more pressure on motorists.
"As an organisation, we are resigned to the fact there will be more speed cameras in the future but we do not welcome them," a spokesman said.
"Speed cameras are sometimes seen as a way of generating revenue instead of its primary function, which must be road safety. And that is unfair on the motorist.
"Only if cameras are well marked and signed in advance do they act as a deterrent, which gives them their place in the road safety plan."
And the RAC says there is the potential for motorists to fool the Specs system by travelling at different speeds between the two cameras.
Spokesman Andrew Howard said: "If a motorist is travelling through a 50mph zone and realises halfway through he is travelling at 60mph, by slowing down to 40mph he can create an overall reading of 50mph.
"It is basic schoolboy mathematics of dividing distance by time.
"However, we do support the Specs system as an efficient method of enforcing a speed limit. When there are roadworks on a motorway, there is a 150pc increase in the accident risk.
"The added benefit of the Specs cameras is they have a highly visible presence which works as a deterrent.
"This is good news for road safety which is good news for motorists."
The Specs system was piloted in the UK in Nottingham where it was deemed a success, leading to a reduction in speeding vehicles of approximately 30pc.
But it was criticised by some road users for being a cynical revenuegenerating scheme and for using intrusive "Big Brother"-style tactics.
The cameras are rented out from their manufacturer, London-based Speedcheck Services.
They were removed from the M6 a few weeks ago following the completion of roadworks from both carriageways between Knutsford and Holmes Chapel. The majority of motorists caught speeding during the trial were issued with fixed penalty notices, ordering them to pay a £60 fine, and were given three points on their licence.
Six people were issued with a court summons for travelling at more than 26mph above the 50mph limit.
A Cheshire Police spokeswoman said: "We caught 200 speeding motorists but we would have hoped to have caught none.
"We would like motorists to have realised the speed restriction is there for a reason, for their safety and for the safety of other motorists and motorway contractors."