Effectiveness of speed cameras in preventing road traffic collisions and related casualties: systematic review

I will check the websites Paul Smith mentions, but the respondents seem most unwilling to acknowledge the crucial and obvious point that fast traffic and people do not mix together so well. The main thrust of UK transport policy for at least the past two decades has been both to separate people from traffic, e.g. to separate the two by pedestrianisation schemes, and, as far as possible, to slow traffic down in urban and residential areas. What is intrinsically so abhorrent about these commonsense policies?

The speed camera is just one more measure designed to slow traffic down. Other measures include speed humps, pelican crossings, road narrowing, one-way streets, blocking off side streets at one end and diverting traffic out of residential areas. These again are all methods of controlling traffic, especially the car, rather than letting our lives be ruined by it in the urban space. Again, what is wrong with that?

The respondents seem resolutely, if not perversely, oblivious to these obvious and commonsense points. They are all designed to separate speeding traffic from people or to divert vehicles onto roads where it is safer to travel at high speed. That has been the clear, and thusfar uncontentious, objective of transport policy for twenty years to my knowledge. As far as I can see these are very sensible policies formulated not to annoy us but conceived in the light of urban traffic hazard, accidents and the need to reduce risk of harm mostly to pedestrians. All these seem self-evident and prudent responses to the need to balance the needs of traffic and people.

Are the respondents going to acknowledge the validity of these points? Or are they going to persist in saying things like: "everyone speeds, and I thank god that they do." For a so-called 'road safety campaigner,' is that not one of the most ridiculous, fatuous and incredibly irresponsible things to say? That is a pretty pathetic argument to try and convince people that fast traffic is safer than slow traffic and that speed cameras *increase* road deaths. How can you argue sensibly with such people?

It is simply ludicrous to believe that speed is an OK pursuit and causes no damage. Try telling that to children, old people, the disabled and other vulnerable pedestrians trying to go about their legal business on busy streets with fast traffic. Yes, of course speed is OK and safer too on motorways, autobahns, autoroutes, freeways and dual carriageways, designed for heavy traffic at high speed, but not anywhere else. I rest my case.

Competing interests: None declared

In answer to Peter Morrell's comment I point out as a rather glaring example the German Autobahn(en), mostly courtesy of Adolf Hitler who also "invented" and promoted the Volkswagen, there are significantly fewer accidents and fatalities on those adrenalin freeing superhighways.

It stands to reason that a free flow of traffic will be less likely to cause close contact, congestion and thus accidents than your neighbourhood roundabouts etc.

Any insurance company will tell you that great numbers of accidents occur in slow speed areas, many if not most accidents happen close to one's home.

Whether speed cameras can cause accidents, which may seem a bit far fetched at first glance, suffice it to say that distractions like naked girls, elephants, a pink hippopotamus or a partly concealed speed camera van at the roadside will prompt most drivers (including innocent ones) to briefly gawk.Which means, of course, that the attention needed on the road is being sidetracked. A further glance in the rearview mirror, wondering whether it did flash and you have a probable cause.

Speed cameras are revenue raiser first and foremost. I am not naive enough to believe that governments, police or many other population groups give a stuff about saving lives.

They allow smoking, don't they.

Competing interests: None declared

It would be very useful if P Smith could actually state to readers in non-obfuscating terms exactly why s/he thinks that roads with fast traffic are safer than roads with slow traffic, and exactly how speed cameras *increase* road deaths--which seems to be the essence of his previous post. That would be a tremendous service, and doubtless a great relief also, to worried and puzzled BMJ readers.

Competing interests: None declared

From the cover through editor’s choice to the article itself and then on to the book review (Traffic Safety) I was both surprised and fascinated to read about speed cameras being considered as a medical issue. I will, therefore, in this response attempt to put the matter properly in that perspective using appropriate medical analogies.

That this piece of work to assess whether speed cameras reduce road traffic collisions and related casualties should find only 14 observational studies that met the inclusion criteria comes as no surprise and, indeed, the level of evidence is admitted and known to be relatively poor with none of good quality yet based upon this the outcome can be a loss of livelihood for the individual which could have greater, more far- reaching and, also, medical consequences. Controversial and divisive, many consider that the real purpose is to raise revenue through fines, almost another stealth tax, rather than reduce collisions and improve road safety. The range of reduction in adverse outcomes reported is, indeed, so great as to call the whole policy into question and underestimates or overestimates of effectiveness cannot be said to show that ‘existing research consistently shows that speed cameras are an effective intervention’.

The book reviewed explains the complexities involved in recommending any road safety measures and that mistakes can be made by researchers using simple methods to try to understand complex and confounding variables, as identified in most of the studies found. The potential for ‘co- interventions’ to have a confounding effect is essentially ignored yet road safety interventions are often multifaceted.

Speeding fines increased from 690000 in 1995 to a projected 4.5 million in 2006 yet the effect of this is uncertain. Fatal accidents have been falling steadily from 1966 (7985) to 3409 in 2000 in any event (unrelated to speed cameras) with little subsequent change beyond a small rise from 2001.

A major concern is the basing of the penalty upon just a single observation (as described by the acting editor) which takes no account of other factors nor any element of (additional) risk. Also, what is targeted is recognised to be responsible for just 7% (or perhaps up to a maximum 15%) of the causes of the road traffic accidents. Too easy to measure, despite speeding being a minority cause, drivers are persecuted by a policy which is unfair in application. Drivers who travel unreasonably slowly create additional risk for other road users and can be prosecuted but this is rare, mobile phone use too seems hardly to have abated. Both these actitvities pose significant danger yet, as police action is required to deal with them, little, if anything is done.

Accidents and deaths in association with police chases are, perhaps, the best examples of speed as the cause. It has been mathematically calculated that the average motorist starting out can expect three bans in a driving lifetime, three opportunities for loss of livelihood and potential medical consequences. The evidence that we, as doctors, are exhorted to access prior to any treatment decision to assist an evidence based approach is at levels higher than that reported here in respect of action(s) to reduce road traffic collisions, injuries and deaths.

No doctor would base any treatment plan on a single observation of any easily measured physiological variable. A single reading of blood pressure, for example, may be abnormally high but a potentially dangerous and lifelong treatment would not be initiated based upon it alone.

I teach in theatre that anaesthetic management must not be based upon one reading of an easily measured variable. Rather, that reading should be considered in conjunction with those of other variables recorded simultaneously and in the context of the whole patient before taking any potentially dangerous corrective action.

A normal blood pressure may be present in the young major trauma victim just ahead of decompensation but we don’t just walk away, rather the whole patient is surveyed to determine the appropriate, usually multifaceted, action.

Obesity is recognized as a major problem contributing to avoidable morbidity and is a significant risk factor for most interventions. BMI recorded at above 30 on four occasions and………….? Consider drug use, cannabis possession of, say, more than X grams might be accorded a fixed penalty which would not vary by the amount and other drugs such as heroin or cocaine in the possession of the individual would be ignored because they were too difficult to measure. If the individual was in possession of other, more dangerous, drugs but had cannabis in an amount Speed cameras may or may not be effective but despite poor evidence and ignoring known confounding variables penalty points are levied.

Fairness and equity were founding principles of the NHS which are currently absent from the subject intervention and should be returned (1). Engagement in burglary, for example, may escape penalty as surrounding and mitigating circumstances are considered. For those who are unfairly persecuted and prosecuted it must be a bit like being transported for stealing a sheep.

1. Lake A, Fair Points. The Sunday Times/Driving. February 8 2004: p.20.

Competing interests: None declared