My name is Magnus Linklater and I am a speed offender. I have just posted off my confession to the magistrate and have entered a powerful plea in mitigation. It will, I suspect, fall on deaf ears. I am, therefore, preparing myself for a hefty fine, the loss of my driving licence, and three months spent discovering a great deal more about our public transport system. There, I've got it off my chest. I feel better already.

The litany of my crimes is not, I think, a lurid one, but I make no defence of it. That 67mph cross-country dash, when the limit stood at 60, will hardly make the record books, but I am, of course, contrite; the failure to observe a 40mph limit in an otherwise empty road does not place me alongside Lewis Hamilton, but it was wrong, m'lud, I admit it; and that last one, whereby I did, as the citation puts it, drive a motor vehicle at a speed exceeding 30 miles per hour, namely at a speed of 40 miles per hour, contrary to the Road Traffic Regulation Act 1984, Sections 81 and 89, though modest as infringements go, marks me out as a serial speedster. I throw myself on the mercy of the court, but with no great expectation of receiving it.

The one thing linking all these offences was that, in each case, I was booked by a speed camera, one of the 6,000 or so spread across our green and pleasant land, and which, as a parliamentary answer revealed this week, are responsible for close on two million fines, raising almost £120 million a year, most of which is spent on... more speed cameras; the number has trebled since Labour came to power.

I would feel worse about my crime spree if I thought that speed cameras were genuinely contributing to road safety rather than catching out idiots like me who fail to notice them. Reading up on them, I see that most clever motorists these days either buy cars that come equipped with camera detection units, or invest in something called a Road Angel (“Guarding your life and livelihood”), which tells you when you are approaching a camera, whether by the roadside or held by a police officer. Both, it seems, are quite legal.

My own observation suggests that motorists simply see speed cameras as occupational hazards, rather than aids to safety. They slow down as they approach them, and speed up as soon as they are past. At least, most of them do, except, obviously, me.

Given this national habit, I am not quite clear how the camera system is cutting road deaths by 100 a year, which is what the Department for Transport claims. In fact, looking at the figures, it seems that their effect is negligible. Despite the massive increase in the number of speed cameras over the past ten years, road deaths have fallen only marginally, from 3,421 in 1998 to 3,172 in 2006. We remain one of the safest countries in the world in which to drive, but I doubt whether this huge investment in technology is responsible. In fact it is not. Looking at the statistics, the biggest safety breakthrough occurred between 1984 and 1994, when road deaths we're almost halved — largely because of better safety standards in car manufacturing — long before speed cameras became the norm.

What, then, do they achieve: apart, that is, from producing a healthy revenue stream? Their main benefit seems to be in relieving police of patrol duties, and herein lies their primary drawback. If motorists know that cameras have taken the place of real people, they grow more, not less, cavalier about their driving. They will deduce that there are fewer officers on the lookout for proper offenders, such as drunken drivers or those without insurance. They will adjust their speed to the camera rather than to the conditions of the road itself. Above all, they will be less vigilant about the things that matter — built-up areas, children coming out of school, pedestrian crossings and so on — and more alert to the things that do not, such as the next approaching speed camera.

This theory, which one might describe as the displacement theory of safe driving, has been given most credence by Paul Smith, veteran campaigner against speed cameras, who argues passionately that their widespread use has interfered with the way that drivers instinctively manage risk — the foundation on which road safety is based. “Speed cameras,” he says, “have changed the things we pay attention to and the things we regard as important.” Instead of focusing on the dangers ahead, motorists feel that they have been relieved of responsibility for managing their own driving, and have ceded it instead to the mechanical intervention of the camera and other traffic signals.

His views are by no means isolated. Experiments in various European cities that have removed rather than added to the plethora of road traffic signs littering their streets have been found to improve safety standards; this is because motorists are thrown back on their own resources and their instincts for careful driving, rather than relying on regulations that may offer guidance but are no substitute for personal initiative.

The thing goes wider still. This year a large Home Office-sponsored survey into the use of CCTV cameras reached a startling conclusion. Far from being the single greatest postwar contribution to public safety, as most councils and police forces claim, they are, on their own, almost valueless. The criminology department at Leicester University examined 13 projects, and concluded that “the majority of the schemes evaluated did not reduce crime, and even where there was a reduction, this was mostly not due to CCTV; nor did CCTV make people feel safer, much less change their behaviour”. Considering that we now spend more than £1 billion a year on CCTV cameras, it might seem legitimate to ask whether this technological emperor is wearing any clothes at all.

I doubt if any of this will help my defence, but I wouldn't half mind trying. “M'Lud,” I would begin, “they say the camera does not lie. It is my intention to demonstrate that it can, and indeed that it certainly does...”

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