The use of 'stealth' speed cameras has led to them being viewed as a revenue raising tool as opposed to a deterrent, according to new research from the Institute of Advanced Motorists (IAM). The warning has come following the release of new grey cameras in place of the previous highly visible yellow ones that were mounted onto stretches of the M25.æ The new cameras have also been introduced on the M1, M3, M6 and M60 motorways. The Highways Agency Digital Enforcement Camera System (Hadecs3) enforces variable speed limits on motorways during periods of congestion, but still targets drivers when the speed limit is 70mph. Tim Shallcross, head of technical policy for the IAM, said: 'The widespread use of mobile cameras, and lately the introduction of fining people for exceeding 70mph on sections of managed motorways, reinforces the perception that they are revenue raisers.î The majority of speed cameras were grey when they were first introduced, but regulation to make them more of a deterrent came in during the 1990s and they were made yellow to increase visibility as a result. 'It is hard to understand why camera partnerships or other safety camera operators are now going back on this policy,î continued Shallcross. 'We have worked hard to promote the safety benefits of cameras and the current tendency to make them inconspicuous risks undoing much of that work.î The Highways Agency has defended the new cameras, however, claiming that they are more visible than the previous grey models, and that there are clear signs in place wherever the cameras are based in order to raise awareness. A spokesman for the Agency said: "Hundreds of thousands of motorists use this stretch of the M25 every day.æThe vast majority are sticking to the speed limits and are experiencing better journeys as a result of smart motorways. 'There are clear signs where cameras are in place and the new cameras are more visible than the previous versions.î Dave Nichols, professional engagement officer for road safety charity Brake, also voiced his disappointment at the change, saying: 'Our own surveys have shown that the majority of people accept that speed cameras do a good job of reducing speeds and saving lives, and almost two in three drivers said more enforcement, including cameras and traffic police, would persuade them to take more care on the road.î