Rapid Responses to:

PAPERS: Paul Pilkington and Sanjay Kinra Effectiveness of speed cameras in preventing road traffic collisions and related casualties: systematic review BMJ 2005; 0: bmj.38324.646574.AEv1 [Abstract]

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Rapid Responses published:

Safe Speed response

Paul Smith   (11 February 2005)

Response to Safe Speed

Paul Pilkington   (11 February 2005)

Time to move the debate on

Paul R Dishman   (12 February 2005)

oxymoron

Andrew G Montgomery   (12 February 2005)

Mental health implications

Paul Oxley   (12 February 2005)

"No Commercial Interest"

Tristram J Torrance   (13 February 2005)

Re: oxymoron /Speed cameras

Hilary Butler   (13 February 2005)

A better use of technology

Steven Ford   (14 February 2005)

A SIMPLE STUDY-STOP AND REINTRODUCE

john s ashcroft   (14 February 2005)

Does this paper enhance the credibility of the BMJ?

Rowland L Cottingham   (14 February 2005)

An illusion of safety?

John P Heptonstall   (14 February 2005)

Re: Does this paper enhance the credibility of the BMJ?

Andy P Langton   (14 February 2005)

Speed cameras are effective?

Keith D Jones   (16 February 2005)

Re: Does this paper enhance the credibility of the BMJ?

John P. Heptonstall   (16 February 2005)

Re: Does this paper enhance the credibility of the BMJ?

Peter A Davis   (16 February 2005)

Comment

Steve Goodacre   (16 February 2005)

A study without bias?

David Dorn   (17 February 2005)

kill your car not a child

James D Woodcock   (22 February 2005)

Re: kill your car not a child

John P Heptonstall   (22 February 2005)

Re: kill your car not a child

Peter Morrell   (23 February 2005)

A (very) carelessly wielded cosh

Alfred P J Lake   (24 February 2005)

Re: kill your car not a child

P Smith   (24 February 2005)

Re: Re: kill your car not a child

Peter Morrell   (25 February 2005)

Re: Re: Re: kill your car not a child

David Dorn   (26 February 2005)

Speed Cameras Are Money Makers First

Dr. Herbert H. Nehrlich   (26 February 2005)

Re: Re: Re: kill your car not a child

Paul Smith   (26 February 2005)

re: kill your car not a child

James D Woodcock   (27 February 2005)

Re: Re: Re: Re: kill your car not a child

Peter Morrell   (27 February 2005)

Re: Re: Re: Re: Re: kill your car not a child

Paul Smith   (28 February 2005)

Automated traffic law enforcement

Ediriweera B.R., Desapriya, Ian Pike, Assistant Professor,Department of Pediatrics   (1 March 2005)

Re: Automated traffic law enforcement

Dr. Herbert H. Nehrlich   (2 March 2005)

A few responses...

David Dorn   (2 March 2005)

Re: A few responses...

James D Woodcock   (3 March 2005)

In reply to James D Woodcock

David Dorn   (4 March 2005)

Re: In reply to James D Woodcock

James D Woodcock   (10 March 2005)

Woodcock and Dorn...

David Dorn   (11 March 2005)

Please keep it factual and on track

Robert A Brookbanks   (18 April 2005)

confounding factors

James B Norwood   (2 May 2005)

Safe Speed response 11 February 2005
Paul Smith, Road safety campaigner / analyst Trac House, Fearn near Tain, Ross-shire, Scotland, IV20 1RR Send response to journal: Re: Safe Speed response	It is a great shame that Paul Pilkington did not reveal his prior opinions nor declare an apparent commercial interest[1]. Given his prejudice, it is extremely worrying that he could find no truly substantial evidence of casualty reductions at speed camera sites. But even if we had excellent evidence of casualty reduction at speed camera sites that would be insufficient to justify the use of speed cameras without also considering effects on drivers across the entire road network. This is a well known problem. Another paper [2] contains the following warning: "Consider system effects. Injury prevention measures may have effects beyond the individual actions they influence directly. These effects may be harmful or helpful. Always consider potential system effects." I am absolutely certain that there are very important and substantial negative "system effects" relating to speed cameras. I have studied how drivers routinely avoid road crashes for 20 years and the four critical factors are undoubtedly: concentration, observation, anticipation and attitude. Speed in excess of a speed limit is never a critical factor unless there is also a shortfall in the critical 4. By and large, drivers make responsible speed choices to the point where causing an injury collision is a once in 150 year experience for the average licenced driver.[3] It is sometimes argued that speed reductions will serve to reduce the severity of "inevitable" impacts. However, real world average impact speeds are far lower than the free travelling speeds that might be effected by speed limits and speed cameras. This is partly because crashes can only take place where there are road hazards and successful drivers routinely slow down where hazards are present. Even after a serious driver error, there is usually time to brake before impact. The effectiveness of braking before impact is most affected by the instant of recognition of the problem, and far less affected by a speed chosen by a responsible driver. In fact speed choice sets the absolute maximum impact speed, while the moment of recognition often enables a crash to be avoided completely. The average is between these two extremes and is far more affected by changes in the moment of recognition than changes in free travelling speeds. The bad news for proponents of speed cameras is that, in practice, they undermine 2 of the 4 critical factors in routine crash avoidance. Observation is undermined because speed cameras encourage much more frequent speedo checking (while an experienced driver does not need to check his speedo at all to drive safely.) Attitudes are undermined because speed cameras are threatening to drivers. We can see one example of a serious attitude effect in the under- researched "race away" crashes described by Chief Constable Richard Brunstrom in a Times article[4]. He said: "We have a particular problem with motorcyclists slowing down for the cameras but then speeding up and dying on the next corner." Another attitude problem is that many drivers may be deluded into considering that a speed choice 'must be safe' because it meets legal requirements. Nothing could be further from the truth - 30mph is potentially a deadly speed. If we were eventually successful at reducing speeds generally the essential process of acquiring driving experience would be adversely affected. [5] Driving experience is closely related to the key component anticipation and also affects concentration and observation skills. The speed camera debate is vast and is far too frequently undermined by oversimplified thinking. It is only when drivers' thought processes and routine accident avoidance strategies are carefully considered that the complete bankruptcy of the technology emerges. <ends> [1] http://ip.bmjjournals.com/cgi/content/full/9/4/293 and http://bmj.bmjjournals.com/cgi/content/full/324/7346/1153/a and http://bcc.gn.apc.org/tbc/2002/winter/speedcams.html [2] http://ip.bmjjournals.com/cgi/content/full/6/2/82 [3] 32million licenced drivers / 214,000 injury crashes in 2003 (source DfT) [4] http://www.timesonline.co.uk/article/0,,2-1215962,00.html [5] http://www.safespeed.org.uk/problem2.html Competing interests: Founder of the Safe Speed road safety campaign.
Response to Safe Speed 11 February 2005
Paul Pilkington, Lecturer in Public Health University of the West of England, Bristol, BS16 1DD Send response to journal: Re: Response to Safe Speed	In response to Paul Smith's insinuation, I can confirm that I do not, and never have had any commercial interests in speed cameras. As a public health professional my overriding concern was to ensure that the best possible evidence around speed camera effectiveness is made available to the public and policy makers. I hope my co-author and I have achieved this aim. Best wishes, Paul Pilkington Competing interests: None declared
Time to move the debate on 12 February 2005
Paul R Dishman, Pharmacist Exwick Pharmacy Exeter EX4 2AD Send response to journal: Re: Time to move the debate on	Dr Pilkington has been unable to provide convincing evidence of the effectiveness of speed cameras yet is advocating more research. We have had speed cameras in use in the UK for over a decade and yet still cannot establish a causal link between cameras and road deaths. It is time to move on from this failed policy and the tired mantra that "Speed Kills" and to press for a better standard of driving. An improved driving test with retesting at intervals would cost money , but would save lives. Competing interests: None declared
oxymoron 12 February 2005
Andrew G Montgomery, General Practitioner St Heliers Auckland New Zealand Send response to journal: Re: oxymoron	The authors state that "Existing research consistently shows that speed cameras are an effective intervention in reducing road traffic collisions and related casualties. The level of evidence is relatively poor, however, as most studies did not have satisfactory comparison groups or adequate control for potential confounders". What if drug companies were permitted to launch their products based upon "relatively poor evidence" and on "studies" without "satisfactory comparison groups or adequate control for potential confounders" ?? It is a fact that many drugs have been launched following thorough double blind case control studies and that these same drugs have subsequently been found to be harmful. I find it bizarre that an otherwise excellent journal should print such nonsense. Competing interests: None declared
Mental health implications 12 February 2005
Paul Oxley, Semi retired accountant Self employed S11 9RA Send response to journal: Re: Mental health implications	Here we have a report advocating speed cameras and lower speeds as an aid to physical casualty reduction. Let us consider the mental health aspect. Some of my local cameras now trigger at 32mph, as confirmed to me by a magistrate who fell foul of a camera on a three lane dual carriageway in an industrial area with few pedestrians. Government tells us that fines are expected to rise to five million per annum, then remain at that level. So, it is not expected that cameras will change driver attitudes. I defy any driver to truthfully claim that he or she does not exceed a limit by a small margin on every journey. Therefore, if we introduce more cameras, virtually every driver is in danger of being caught and penalised. The potential for huge numbers of banned drivers is real. In the case of those who must drive to earn a living, the risk to their mental wellbeing is considerable. Loss of licence can lead to loss of employment, loss of house and family breakdown. And for what? Being caught travelling at 32mph four times in three years? This is a ludicrous notion. Another health aspect of lower speeds is that of concentration loss. Since the introduction of speed limiters in heavy goods vehicles, the soporific effect of attaining, and holding, a particular speed has led to more crashes as drivers fall asleep at the wheel. I used to drive in pre speed limit times. Traffic was light and I travelled the length of the M1 legally at speeds in excess of 100mph. I never lost concentration. I never felt the onset of drowsiness. Now restricted to 70mph, the opposite is true when the road is clear. We have one of the best road safety records in the world, but one that has deteriorated since the introduction of speed cameras, for which I can find no other explanation. Indeed, figures published by the Royal Society for the Prevention of Accidents tell us that more people die in domestic accidents than die on our roads. The report quotes worldwide casualty figures. I would suggest that corrupt countries with poor discipline make a major contribution to those figures. Here, cameras are irrelevant as basic safety attitudes are absent. In conclusion, I would suggest that no claim for the effectiveness of speed cameras can be upheld in the light of Government's admission, via Alistair Darling, that 743 camera sites saw, “casualties increase rather than decrease” and many others saw no change. Competing interests: None declared
"No Commercial Interest" 13 February 2005
Tristram J Torrance, Office Manager Witney, Oxfordshire OX28 6HT Send response to journal: Re: "No Commercial Interest"	I am quite prepared to believe Paul Pilkington's assertion that he has no commercial interest in speed cameras. Although I was a "civilian" in this particular battle, I watched it with interest for some years, as it was becoming obvious that my driving licence and livelihood were becoming increasingly at risk from speed cameras. This despite the fact that I was a highly trained professional driver, who always drove in what I felt (and had been trained to believe) was an entirely safe manner. I studied the figures, the arguments and the statistics from both sides, and was more convinced by those of the ABD and Safe Speed than by those of the Camera Partnerships. As a result of this, I joined the ABD. The proponents of speed cameras face two problems which they cannot overcome. The first is a simple lack of credibility of their case as they state it. No matter what statistics are quoted, it is manifestly obvious to most drivers that many speed limits are incorrectly set. It is equally obvious to them that the actual distraction involved in attempting to stick exactly to a speed limit is far more dangerous than the possibility that one might be travelling slightly below or slightly above that limit. It is also obvious to any driver that speed limits cannot possibly reflect road conditions, which can change within yards, due to the presence of a fixed, or temporary, or mobile hazard, weather, or anything else. Most drivers are far from stupid - they know all these things, and they very sensibly drive at a speed which they consider to be safe for the circumstances and conditions at the time. The second problem faced by the camera lobby is the lack of complete honesty with which the campaign which has been waged by the Speed Camera "Partnerships" (normally made up of the local council, police, and magistrates, plus camera partnership staff). For years they have stuck to their assertion that most of the vast sum of money raked in by the cameras is sent to the treasury, and that they, and the police, receive no "profit" from the cameras. This may well be true in an absolutely strict sense, but it is of course duplicitous to say the least. Prior to the cameras, the police made a loss on speed enforcement - it cost them resources to carry it out, and they did not receive the fines. This meant that they really pursued only the cases that they felt really warranted it, and did not bother with minor infringements. Now, they have their costs of enforcement returned to them, and they also have much of that enforcement carried out by civilian staff, who they do not have to pay for. This means that they have greater resources left over than they had before. In other words, they have "profited" from the current regime.The fact that those resources appear to be being wasted is a separate argument, but is nonetheless, most annoying to those who have seen through the spin. Prior to the cameras the speed camera partnership staff's jobs did not exist at all. This truism needs to be stated, as it is one of the prime wreckers of their argument. It is quite obvious to anyone that the very people who make the claims about profits not being made, have jobs only because they are paid for out of camera revenue. A quick glance at the advertisements for the jobs show some very attractive salaries and packages including company cars and other benefits, particularly on the PR side. These growing empires of bureaucrats and PR mouthpieces ALL depend for their very livelihoods, on camera income. The fact that this particular cash is labelled as "operational expenses" rather than "profit" is a pretty poor fig-leaf for some very handsome nest-feathering. Again, most drivers are not stupid. They are quite capable of working all this out for themselves, and they have done so. The partnership PR's can excitedly quote statistics showing almost universal approval for the cameras as much as they like. It has as much credibility as the Emperor's new clothes, and the spin is just as transparent. One problem with the camera debate is its sterility, as both sides can and do draw from endless statistics to prove each other wrong, in a truly dull game of tit for tat. The thing about this, and a very good thing really, is that faced with it, the public will make up their own minds. It ids clear that they have largely done so, and the days of the camera partnerships are almost certainly numbered. Following the camera farrago, many members of the public will never again believe that they are travelling at a dangerous speed until they are told so by a wise old copper by the roadside, who has just pulled them over, explains why, shows them the hazard that they might have overlooked, and whose job clearly does not depend on that particular conviction. Roll on the day. Competing interests: Member of the Association of British Drivers
Re: oxymoron /Speed cameras 13 February 2005
Hilary Butler, freelance journalist home 1892, New Zealand. Send response to journal: Re: Re: oxymoron /Speed cameras	Dear Sir, I would like to agree with andrew Montgomery who said: >>>> What if drug companies were permitted to launch their products based upon "relatively poor evidence" and on "studies" without "satisfactory comparison groups or adequate control for potential confounders" ?? It is a fact that many drugs have been launched following thorough double blind case control studies and that these same drugs have subsequently been found to be harmful. I find it bizarre that an otherwise excellent journal should print such nonsense. <<<<< I'd like to go two steps further. Neither my husband or myself have ever had a speeding ticket or been "caught" by a speed camera. However recently, we were rung by the Police who wished to talk to us about complaints they had received from two members of the public from mobile phones. It seems that on a journey from Thames back home, while studiously observing the speed limit, we were a major source of road rage for certain people who live to get between A and B at speeds exceeding those "allowed". The only parts of the road where we did not experience the fronts of cars up our rear end, were areas notorious for the placement of mobile speed cameras. The officer politely told that we should be driving in a manner so as not to inconvenience the majority on the road. Given that we were possibly the only car adhering to the specified limit, we pointed out the "contradiction" of such advice to the officer concerned, who didn't really know what to say. Then, this week, our son, on his way home from a specialist appointment was pulled over by an officer. Yes, he drives a black, sleek, potentially fast, low slung "batty", so stands out like a sore thumb, and probably catches the eye of those who look out for frothing boy-racers. At the time he was first tailed by the officer he was being overtaken by many other vehicles on the road. He was issued a ticket for doing 113 km an hour on a 100 km stretch, while all others around him sailed on at greater speeds with impunity. Had he been driving our old bomb, the only thing he might have been pulled over for, would have been a warrant check. The fact is that speed cameras don't contribute to anything by revenue collection. The real problem is people's attitudes to driving, and,.... in our son's case, officers' preconceived ideas about models of cars, and their occupants, while ignoring more worthy recipients of the police's attention. Hilary Butler. Competing interests: None declared
A better use of technology 14 February 2005
Steven Ford, GP Haydon & Allen Valleys Medical Practice Send response to journal: Re: A better use of technology	Sir Fewer cars on the road, better standards of driving by all, requalification at regular intervals, intelligent setting of limits and thoughtful application of the law would all help. Until this improbable combination of circumstances arises: In even the most humble of modern vehicles it is genuinely difficult to creep along at thirty miles per hour for extended periods of time. I would welcome the provision of a finger tip toggle switch to adjust a voluntary speed limiter in five mph increments up or down. Then I could keep my eyes on the road rather than glued to the speedo. Are any manufacturers reading this? Steven Ford Competing interests: three, now lapsed, speeding tickets
A SIMPLE STUDY-STOP AND REINTRODUCE 14 February 2005
john s ashcroft, General Practitioner DE7 8DY Send response to journal: Re: A SIMPLE STUDY-STOP AND REINTRODUCE	It is clear from responses that there is considerable uncertainty around the benefits or not of speed cameras. There has been a seven fold rise in fixed penalty fines from 2000-01 to 2003-4 (1), but the death rate on our roads didn't fall; infact they increased from 3,409 to 3,508 over the same period. (2) Though there is evidence of an effect when safety cameras are placed on a road, regression to the mean may account for much or all of the apparent effect. There is obvious concern that the criminalisation of millions of citizens, who previously considered themselves law abiding, with tens of thousands of them losing there licence to drive, may have adverse consequences as diverse as undermining support in the police, increased stress, or marital disharmony. Even a small increase in suicide or heart disease rates in those convicted may negate any conseiveable benefit. Maybe the £91.9 million (1) spent on in the installing and running of the cameras in 2003-04, could have been better spent by society? A recent poll of visitors on the web site "crimereduction.gov.uk" ( a site unlikely to be frequented by "boy-racers"), asked if they thought speed cameras improved road saftey..43% said yes, and 53% said no. Fortunately there is a simple way to help clarify matters. I propose that the use of all speed cameras are suspended for one year, and then reintroduced; and the effects observed. As a doctor I use this technique frequently to confirm or deny effect or side effects of drugs I prescribe, others would call it an interventional study. 1. Daily Telegraph 2.2.2005 2. Road casualties in Great Britain 2003, Transport Statistics Bulletin,National Stationary Office Competing interests: None declared
Does this paper enhance the credibility of the BMJ? 14 February 2005
Rowland L Cottingham, Consultant in Emergency Medicine Brighton and Sussex University Hospitals NHS Trust BN2 5BE Send response to journal: Re: Does this paper enhance the credibility of the BMJ?	I have to ask how this weak paper got through the referees. It is an uncritical non-metaanalysis, which the authors claim to be systematic, of 14 observational studies. The best paper is type 3 evidence, most are worse. "In terms of methodological quality, we classified no studies as being good quality, 7 as average, 2 as average-poor and 5 as poor." A statistic that is conspicuous by its absence is the change on road deaths. As an example, the overall UK trend is static between 1992 and 2002, the most recent figures available(1). Even worse, road deaths have risen in some groups such as motorcyclists and their passengers since 1992, as well as car drivers and occupants, although less dramatically, since 1998. How does that fit with the hypothesis that cameras reduce casualties? Nowhere are there actuarial figures showing what is happening to collisions as a whole in countries where cameras have been introduced. Surely this is available from insurers? The British Medical Journal compound the error by plastering the front cover with "Effectiveness of speed cameras. They reduce crashes and related casualties." The paper does not prove either of these assertions. We would all like to see fewer casualties and collisions. A paper of such poor quality does nothing to improve the debate and has, in my view, badly damaged the BMJ's credibility. 1.http://www.statistics.gov.uk/STATBASE/ssdataset.asp?vlnk=4031 Competing interests: None declared
An illusion of safety? 14 February 2005
John P Heptonstall, Director of The Morley Acupuncture Clinic Leeds LS27 8EG Send response to journal: Re: An illusion of safety?	Sir The authors' attempt to speculate positively on the justification of speed cameras in terms of public safety, whilst acknowledging that the evidence for safety appears to be minimal at best, ignores (as do all systematic reviews) specific cases like the one cited on TV a couple of months ago. A Chief Constable (from the North East if my memory is correct) reported that for his area of operation speed cameras appear to have increased the death rate. Perhaps one could speculate on why this might be, and what are government and speed camera enthusiasts doing to reduce the negative impact of such cameras in that, and other "less safe", police areas? Regards John H. Competing interests: None declared
Re: Does this paper enhance the credibility of the BMJ? 14 February 2005
Andy P Langton, ABD Regional Coordinator ABD Send response to journal: Re: Re: Does this paper enhance the credibility of the BMJ?	I share these same concerns we are seeing shoddy government and non- government research in this area. Now we have research being presented based on that same shoddy research. However, in this research it clearly and correctly identifies that those studies that this research is based on are substandard. “In terms of methodological quality, we classified no studies as being good quality, seven as average, two as average-poor and five as poor” in itself not a good start. Then re-affirms this in the figures quoted. “The reduction in adverse outcomes in the immediate vicinity of camera sites varied considerably across studies, with ranges of 5-65% for collisions, 12-65% for injuries, and 17-71% for deaths at camera sites” – these comments says nothing more than the combined published research as it stands can only really be considered inconclusive at best. But, in the conclusion is still unable to say as much and states. “Published results consistently shows the effectiveness of speed cameras in preventing road traffic collisions and injuries” Where’s the consistency, where's the effectiveness?? Further, PA Consulting Group's research is given a quality score of 6 (average) yet this published government funded research costing £1.7 million (now there's a conclusion bending incentive if I ever saw one) does not even go as far as to factor out RTTM error in their figures. I can quite imagine that the other research is equally flawed since all of the research I have seen on speed cameras takes the approach of 'giving a possible solution a problem' rather than 'finding a solution to a known problem' and any scientist or engineer worth their salt knows this is the wrong way to do things. So does this paper enhance the credibility of the BMJ? - I think not. In fact worse it gives science a bad name. Competing interests: True road safety and the decriminalisation of decent motorists.
Speed cameras are effective? 16 February 2005
Keith D Jones, Clinical Nurse Specialist Challenging Needs, Sexuality and Offending 1 Oak Glade, Off Chertsy Road, Epsom, Surrey KT19 8NW Send response to journal: Re: Speed cameras are effective?	I notice that Paul Pilkington’s paper “Effectiveness of speed cameras in preventing road traffic collisions and related casualties: systematic review” has attracted some comment about the poor quality of data used. Others have drawn attention to the many failings of the study and there is no need to repeat these points here. However I am struck by something so far unmentioned. Although Mr. Pilkington recognizes some of the shortcomings of his study the BMJ does not make this clear on its website, where it announces that “Speed cameras are effective” and “Speed cameras prevent collisions and casualties”. I realize that the horse has probably bolted by now but would ask you to review these statements with a view to changing them so that they reflect the degree of uncertainty of the findings of the study. Competing interests: None declared
Re: Does this paper enhance the credibility of the BMJ? 16 February 2005
John P. Heptonstall, Director of the Morley Acupuncture Clinic Leeds LS27 8EG Send response to journal: Re: Re: Does this paper enhance the credibility of the BMJ?	Sir Agreeing with Rowland Cottingham wholeheartedly I would add that the meta-analysis seems to take into account an inordinate number of overseas studies as examples of how speed cameras might affect mortality and morbidity statistics in the UK. Does this mean that we have virtually no effective studies from UK Police authorities that are capable of scientifically assessing the effects of said cameras; such that Government propaganda constantly fed the public about the overall benefits outqweighing risks has no scientific support in terms of studies performed in the areas of operation of UK speed cameras? What have speed cameras and strategies for deployment in Australia, Beijing, British Colombia, the USA and Kuwait - where rules of the road, shapes and sizes of roads, police procedures and process, legislation and motoring/driver cultures are different from those of the UK - got to say about policing and road use in areas of the UK which themselves can offer quite diverse advantages and disadvantages for the deployment of such technology? When at least one Chief Constable is on record as stating that speed cameras in his area have increased mortality/morbidity and we have no local evidence of value, it would appear that this government have unleashed an expensive - perhaps lethal - tool on the unsuspecting public which foots the bills without sufficient justification. Studies should have been performed which evidenced their safety and efficiency before massive, perhaps cynically for financial reasons, deployment of so many potentially lethal objects on our roads and streets. One part of Leeds, Horsfort/Rawdon, is said to sport about 12 such cameras within a mile or so - clearly the police do not have scientific support for such a concentration of expensive, perhaps anti-social, equipments? Regards John H. Competing interests: None declared
Re: Does this paper enhance the credibility of the BMJ? 16 February 2005
Peter A Davis, Specialist Registrar, Histopathology Broomfield Hospital, Court Road, Broomfield, Chelmsford, Essex CM1 7ET Send response to journal: Re: Re: Does this paper enhance the credibility of the BMJ?	I wholeheartedly agree with those who have quite rightly criticised this fundamentally flawed paper's inclusion in the BMJ, and raised concerns regarding the refereeing process that lead to its inclusion. Even more worryingly, the decision to indulge in front-page headlines that are simply not supported by the paper itself surely calls the editorial judgement of the BMJ into question. Sadly, this tabloid-esque behaviour appears to be a growing trend, giving the impression that the BMJ is more interested in grabbing headlines in the general media than ensuring the very highest quality of scientific research. Unless the vetting of submitted papers is improved, the BMJ is in grave danger of becoming an embarrassment to the profession. Competing interests: Once caught by a mobile speed camera unit.
Comment 16 February 2005
Steve Goodacre, Senior Lecturer University of Sheffield Send response to journal: Re: Comment	Some correspondents have criticised the BMJ for publishing “poor quality” data. Leaving aside the subjectivity in this judgement, the principal criteria for publication should be the importance of the topic. If it is an important topic (an few would disagree that it is) then surely the BMJ has a duty to publish the available scientific evidence? We may be concerned (as the authors are) that the evidence is not very reliable, but only by publishing the evidence can we have the opportunity to make a judgement. The only alternative seems to be to suppress the data. Is that what you are demanding? As regards the quality of the data, simply pointing out potential alternative causes for the observed findings, such as confounding or regression to the mean, does not automatically invalidate the findings. All research studies (including randomised trials) have possible alternative explanations for their findings. The true skill of critical appraisal involves considering potential flaws and determining which potential explanation is likely to be responsible for the observed findings. It is surprising that some correspondents seem to value the anecdotal comments of a Chief Constable and their own random observations above systematically collected data. For all its shortcomings, this study may represent the best evidence that it is reasonable to expect. Indeed this evidence is rather better than that usually available to support safety interventions or even many health care interventions. Ideally we should undertake a randomised controlled trial of speed cameras, but there are good reasons why randomised controlled trials are rarely performed in these circumstances. As someone who is currently undertaking a randomised trial of a population -level intervention I can testify to the huge challenges involved. It’s all very well demanding high quality evidence, but you need to be prepared to support randomised trials. My experience is that few people are. Finally, aren’t we forgetting that the principal purpose of speed cameras is to allow the police to enforce the law. If you don’t like the law, then campaign to get it changed, but don’t complain when the police decide to enforce it. If there is scientific evidence that enforcement leads to reduced crashes and injuries (as Pilkington’s study seems to show) then that is a bonus. Competing interests: None declared
A study without bias? 17 February 2005
David Dorn, Freelance Journalist Durham DH4 Send response to journal: Re: A study without bias?	I quote from a letter by one of this study's authors (Pilkington): "I have for the past five months been working on a systematic review to evaluate the effectiveness of speed cameras at reducing deaths and injuries. The study is due to be completed in the next month or so. Although there are methodological issues to take into account, premilinary results show positive results for speed cameras. Hopefully the results of the review will provide definitive scientifc evidence of their effectiveness." One would hope that the BMJ has enough nous to thoroughly vet its contributors and their contributions for bias - however, it would seem to have fallen down badly in this case. I trust that peer review will satisfactorily nullify any effect this paper has, although I expect that the likes of Transport 2000 will already have picked up on it. However, for those who have not done the required searches, test Mr Pilkington's bias or lack thereof by reading his letter at : http://bmj.bmjjournals.com/cgi/eletters/324/7346/1153/a#22229 Competing interests: None declared
kill your car not a child 22 February 2005
James D Woodcock, Research Student, LSHTM London WC1E 7HT Send response to journal: Re: kill your car not a child	It is always amazes me the righteous indignation of people who engage in the most dangerous and anti social legal activity – driving- and then argue that they should be able to break the few laws that restrict their dangerous actions with impunity. We need to put some context on the harms of the car society which is sadly missing from most of these speedophile comments. Firstly remember globally motorvehicles kill 1.2 m directly on the roads every year. Mostly these are pedestrians and cyclists in poorer countries. In Britain 3500 people are killed a much lower rate but still a horrific number, that is more than died on September 11th 2001. Why is the rate lower in Britain? It is not primarily because the danger on the roads is less but the exposure is less, as over time fewer people walk and cycle due to the danger. One indication of this is that the injury rate in the 10-14 year age group has fallen least as kids of this age have probably changed behaviour least. This driving of others off the roads is the most obscene theft of public space by exposing others to danger. It is a form of terrorism. It also replaces healthy methods of transportation with unhealthy ones. I tried a country walk the other week in which the right of way went over a dual carriage way with no crossing. I turned back and so did not get killed, this does not mean the road was not dangerous. Walking and cycling are good for physical and mental health, car driving is good for big business health. Cars consume massive amounts of land in our cities. They promote sprawled development that harms accessibility for shops, jobs and services all those without cars. They are expensive not because of taxation, which is less than the cost of the harms drivers impose on others, but because they are a inherently expensive and inefficient means of transportation. It has been calculated the speed of a car per hour (allowing for time to work to earn the money) is similar to a bike. Car and trucks are a major contributor to global warming and in the here and now to the deaths of millions from air pollution. They are the biggest cause of noise pollution and communities severance, both risks for poor mental health. All of the harms and benefits are very unequally distributed, with the benefits going to richer car drivers and big business and most of the harms to the poor, disabled, children and the elderly. Are speed cameras an effective response to this scale of harms? No of course not. But when society is not even willing to consider more drastic measures, like cars with built in restrictions or heaven forbid banning the car and giving streets back to people, then speed cameras are the best we get. Don’t forget speed cameras are introduced because drivers regularly speed, and a faster speed means longer stopping time and worse results in a crash. This behaviour may be very common but that does not stop it being far more of a dangerous social problem than all the things we are told to worry about like gun crime or teenage gangs. James Woodcock Competing interests: None declared
Re: kill your car not a child 22 February 2005
John P Heptonstall, Director of the Morley Acupuncture Clinic Leeds LS27 8EG Send response to journal: Re: Re: kill your car not a child	I agree with much of James's content but he forgets, some some speed cameras may be the cause of increased fatalities and injuries in certain regions and ought to be removed where that is the case. Until UK studies support the use of speed cameras - clearly at present the jury is very much out on this (witness the study the authors bring) - the UK ought to initiate proper studies, nationwide, to acertain which cameras are offensive and which are beneficial. Regards John H. Competing interests: None declared
Re: kill your car not a child 23 February 2005
Peter Morrell, Hon Research Associate, History of Medicine Staffordshire University Send response to journal: Re: Re: kill your car not a child	I agree with just about everything James Woodcock says about speeding traffic and accidents and the desirability of some method of reducing traffic speeds most especially in urban areas. I think also that previous respondents have missed the main point that roads with fast traffic are likely to be much more dangerous than roads with slow traffic. Speed cameras are quite simply a device to slow traffic down to reasonable speeds. Therefore, it logically follows that they are designed to make the roads safer. This is surely more commonsense than 'science.' The only big disadvantage I have noticed with speed cameras is that they tend to reduce clustering of vehicles in short pulses, and this means the cars tend to come along in great, long evenly spaced streams. That is a problem if you want to cross a road as a pedestrian--you are likely to have to wait far longer for a gap to appear. Also, if you wish to turn into the traffic from a side street, then again it takes much longer. Of course, the advantage is that the stream of traffic is moving at a slower average speed than before the cameras were in place. On balance, I would therefore say that speed cameras have more advantages than disadvantages and, as James Woodcock says, they make roads safer by reducing traffic speeds. I also agree that they are abused as a lucrative source of easy income by local government and they are becoming enforced by police officers sat in mobile camera vans usually placed only yards from the actual speed limit signs, which is bad for police-public relations. Competing interests: None declared
A (very) carelessly wielded cosh 24 February 2005
Alfred P J Lake, Consultant Anaesthetist Glan Clwyd Hospital, LL18 5UJ. Send response to journal: Re: A (very) carelessly wielded cosh	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
Re: kill your car not a child 24 February 2005
P Smith, Road Safety analyst / campaigner Safe Speed campaign, IV20 1RR Send response to journal: Re: Re: kill your car not a child	James makes the mistake of confusing transport ideology objectives with road safety objectives. Speed cameras are neither intended nor suitable as instruments of change in transport ideology, and I'm quite sure that if the public believed that their purpose was to promote 'modal shift' they would be considered utterly unacceptable. Speed cameras must be justified on road safety grounds alone - the question that must be answered is: "do they make the roads safer overall?" Having personally spent over 8,000 hours studying the subject, I am absolutely certain that they do not. It is by no means obvious that transport safety could be much improved by encouraging different transport modes. For example, buses are around ten times more dangerous to pedestrians than cars [1]. Total rail transport risks are comparable to car risks (but you have to add back in railway trespassers that are usually excluded from the figures). If we went back to horses (!) the death toll would be many times higher and transport would be many times less efficient. It is extremely difficult to imagine a policy intervention that would be acceptable to the public and the requirements of commerce that would even significantly reduce the growth of motor traffic. John Prescott said in 1997: "I will have failed if in 5 years time there are not fewer journeys made by car." Yet motor traffic continued to grow at its long term rate of +8.75bvkm per annum. [2] It's also notable that every advanced economy in the world has developed a similar 'car dependence' based on free market choice. Clearly our duty to road safety is to use cars as safely as we can, and to do that we have to scrap speed cameras. See: 'The Case Against Speed Cameras' [3] Best regards, Paul Smith, Safe Speed http://www.safespeed.org.uk [1] http://www.safespeed.org.uk/pedrisk.html [2] http://www.safespeed.org.uk/smeed.html [3] http://www.safespeed.org.uk/againstcameras.doc Competing interests: Founder of the Safe Speed road safety campaign
Re: Re: kill your car not a child 25 February 2005
Peter Morrell, Hon Research Associate, History of Medicine Staffordshire University, UK Send response to journal: Re: Re: Re: kill your car not a child	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
Re: Re: Re: kill your car not a child 26 February 2005
David Dorn, Freelance Journalist Durham DH4 Send response to journal: Re: Re: Re: Re: kill your car not a child	Peter Morrell poses the question: " why [ ] roads with fast traffic are safer than roads with slow traffic, and exactly how speed cameras *increase* road deaths." Statistically, motorways and non-urban dual carriageways are the safest of our roads - deaths per mile/thousands of vehicles are far fewer than in urban roads and 30mph limits. This is most likely because there are fewer pedestrians on fast roads - many fewer. It's also due to the opposing flows of traffic being separated by a central reservation and armco barriers - the potential for head-on collisions is drastically reduced. The "fast" roads also have "safe" design speeds in excess of 100MPH, making travelling on them at speeds up to and including that a relatively low-risk proposition for a capable driver. In urban scenarios, however, a posted 30MPH limit may be totally inappropriate for the conditions - yet we are exhorted to "stick to the limit". There are many, many sections of urban roadway where it would be extremely foolish to travel at 30MPH, and yet that's exactly the behaviour that all the "Safety" camera campaigns encourage. It would be far more effective to educate drivers properly in the first place - that they should be acutely aware of road conditions, pedestrians, and, indeed, anyone/thing else that may be put at risk as a result of their presence. The problem is, though, that as we automate traffic policing, the need for a driver to observe and react is diminished - the rule is now "30 is safe, 33 gets me a ticket" or "Go on green and don't chance it (even at 3am when everyone else is abed!)" As more an more automated traffic controls are introduced, the need for a driver to think (and hone his driving skills) is reduced. Many roundabouts are now controlled by traffic lights - so the need to learn to merge into a stream is reduced - the knock-on effect being people who no longer match the speed of the traffic on a fast road sliproad, but expect the traffic already there to move over and allow them to enter at a speed differential of maybe 20mph slower. Here's a (not altogether serious) thought - rather than keep introducing all of these "safety" measures, why not introduce a "risk" measure - and place a nine inch spike where the driver's airbag would normally be, such that if he impacts anything (human or static) frontally, it detonates and skerwers him straight through the heart. What effect does Peter Morrell think *that* would have on driver awareness and risk assessment? Competing interests: None declared
Speed Cameras Are Money Makers First 26 February 2005
Dr. Herbert H. Nehrlich, Private Practice Bribie Island, Australia 4507 Send response to journal: Re: Speed Cameras Are Money Makers First	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
Re: Re: Re: kill your car not a child 26 February 2005
Paul Smith, Road safety analyst and campaigner Safe Speed IV20 1RR Send response to journal: Re: Re: Re: Re: kill your car not a child	Peter, You might find it helpful to read the references offered. Or for greater depth explore the Safe Speed web site which is now well over 350,000 words. Road safety is an extremely complex matter and attempting to reduce it to vehicle speeds in relation to a speed limit turns out to be an absurd and dangerous over-simplification. We don't need faster traffic or slower traffic. Speed cameras haven't even delivered slower traffic. What they have delivered is a truly frightening array of side effects [1][2] including less attention to the road ahead, serious damage to the Police / public relationship and a distortion of safety priorities. We need to improve the performance of the system by making it more error tolerant and by improving the performance of the average driver. Improving the performance of the average driver is most easily accomplished by identifying and attacking the worst 10%. And no - speed cameras are not even effective in identifying any group of drivers. Everyone speeds, and I thank god that they do. [3] [1] http://www.safespeed.org.uk/dangers.html [2] http://www.safespeed.org.uk/speedo.html [3] http://www.safespeed.org.uk/why.html Paul Smith, Safe Speed, http://www.safespeed.org.uk Competing interests: Founder of the Safe Speed road safety campaign
re: kill your car not a child 27 February 2005
James D Woodcock, Research Student LSHTM Send response to journal: Re: re: kill your car not a child	The most frequent response to my posting is that cameras are only justified if they reduce injuries and deaths. While I am a keen supporter of researching the health impacts of policy interventions, I think it is important to ask why speed cameras are required to prove themselves in a way that other law enforcement measures are not. The ‘war on drugs’ is expensive with negligible evidence of harm reduction. CCTV cameras constantly watch pedestrians, again with little evidence of any social benefit. One could argue that speed cameras at least signal that the law is now also taking a ‘zero tolerance’ approach to dangerous driving. And the evidence weak as it is, does at least point in the direction in reduction in harm. A further issue is that the cameras might produce slower speeds and hence more road use by pedestrians and cyclists. This could lead to more injuries but lower injury rates. This shows the problems with focusing on reducing injuries/deaths without challenging car dependency. An increase in pedestrian injuries could paradoxically be part of an improvement in population health if it occurred due to a substantial increase in walking. But traditionally, responses to the danger posed by cars is to remove other road users –forgetting all the other health benefits of a modal shift including air pollution, equity, human rights, resource use, noise, and climate change. But of course Paul Smith refuses to see driving fast as an issue at all. While he pretends to be a road safety campaigner he is in fact an ideologue for drivers knowing best and fast driving. Searching his website there are not many recommendations to improve safety apart from removing speed cameras. One issue he does raise is about driver attention. Concerning road safety in the UK he says “Actually it's pretty good - we might have inattentive drivers, but don't forget we already have the safest roads in the world - so they can't be that inattentive most of the time.” So he does not really think there is a problem. He does mention a few sources of distraction, “Distractions might come from passengers, telephone calls, roadside billboards (to name a few).” However, no where does he consider that mobile phone use rather than speed cameras might be the reason road deaths are now falling less quickly than they were. Clearly the law on phones is widely ignored and police enforcement and penalties pathetic, so why not challenge this? His theory also centres around a few bad drivers. Good news for most drivers, particularly when surveys show the vast majority think they are better than average. He fails to recongise how small increases in risk by the average driver (by say going a few miles an hour faster) result in a lot more crashes and more serious crashes overall. He also calls for more driver education not remembering the best evidence from a Cochrane systematic review shows, “This systematic review provides no evidence that post-licence driver education is effective in preventing road traffic injuries or crashes.”[1] In his most recent posting he call for the roads to be more ‘error tolerant’, this is a cover for promoting safety by driving pedestrians and cyclists of the roads. On the question of revenue, financial penalties aimed at stopping harmful behaviour always produce the risk that authorities have an interest in maintaining the behaviour. It would also apply to taxes on smoking. A more equitable solution would be to more readily ban drivers, which would less disproportionally affect poorer drivers. If you think life would be impossible without your car, think how difficult is life in a car dependent society for the many people without cars now, such as children and many elderly people? And of course drivers always have the choice of not speeding. Paul Smith claims that buses are ten times more dangerous to pedestrians than cars. But his figures are per vehicle mile, not per passenger mile. Buses carry far more people than cars (usually more than ten times more) so this point is seriously misleading. It should also be noted that cars promote sprawled patterns of living that increase distances travelled, like L.A. Any comparison in terms of km travelled will miss the greater distance necessitated by car dependency. Buses also operate in areas of higher population density than cars making pedestrian injuries more likely. Parked cars also represents a significant increase in risk of being hit by any kind of vehicle, including of course buses. I would be interested to see where he is getting his improbable sounding figures on rail safety from. I do hope he remembers to put rail deaths due to cars on the line as caused by cars not rail! However, his most entertaining assertion is that “It's also notable that every advanced economy in the world has developed a similar 'car dependence' based on free market choice.” This is fundamentally flawed because of two assumptions. Firstly, that free market choice provides what most people want, and secondly that we have actually seen a free market. Free market choice means that cars are able to impose danger on more vulnerable road users thereby intimidating them into using a car or stop using the road altogether. An individual car is also faster than a bus but the greater number of vehicles necessary for car as opposed to bus travel means all vehicles are slowed down. Therefore, every individual is rational to switch to a car but everyone ends up worse off than before. As mentioned already car travel also promotes sprawled land use that makes public transport less efficient and walking less suitable. Secondly, the free market was very much assisted by corporate interests and friends in government. Did the free market pay for the roads? In the USA a combination of General Motors and Firestone tyres bought up and destroyed the finest tram systems in the world and replaced them with inferior buses. This was officially recognised in the Snell report. Similar processes occurred in many countries. What we have seen is not a free market but corporate capitalism producing inefficient and dangerous transport that benefits no-one except the corporate interests. These include car firms, oil, construction, advertising, banking, metal, rubber, and firms that benefit from cheap long distance goods travel by road- such as supermarkets. So no wonder that New Labour has not reduced car use as it is has failed to challenge corporate interests here as elsewhere. [1] http://www.update-software.com/Abstracts/ab003734.htm Competing interests: None declared
Re: Re: Re: Re: kill your car not a child 27 February 2005
Peter Morrell, Hon Research Associate, History of Medicine Staffordshire University, UK Send response to journal: Re: Re: Re: Re: Re: kill your car not a child	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
Re: Re: Re: Re: Re: kill your car not a child 28 February 2005
Paul Smith, Road safety analyst and campaigner Safe Speed, IV20 1RR Send response to journal: Re: Re: Re: Re: Re: Re: kill your car not a child	Peter, you wrote: "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?" PLEASE read the references offered. Competing interests: Founder of the Safe Speed road safety campaign
Automated traffic law enforcement 1 March 2005
Ediriweera B.R., Desapriya, Research Associate Department of Pediatrics,BC Injury Research and Prevention- University of British Columbia-V6H 3V4, Ian Pike, Assistant Professor,Department of Pediatrics Send response to journal: Re: Automated traffic law enforcement	Automated traffic law enforcement is designed to reduced traffic crashes and improved adherence to traffic laws through the use of photographic and electronic technology. The objective of automated traffic law enforcement is reduced traffic crashes resulting from improved adherence to traffic laws achieved by effective deterrence of potential violators which could not be achieved by traditional law enforcement methods. Photographic detection devices are used extensively in many other countries including Australia, Austria, Belgium, Canada, Germany, Israel, the Netherlands, Singapore, South Africa, Switzerland, Taiwan, and the United Kingdom. (1) Police forces in many motorized countries in the world claim that these systems are a great addition to their enforcement strategies. (1) It is difficult for police to enforce red-light respect because they must follow offenders through the light in order to catch them. This can endanger other motorists, cyclists and pedestrians as well as the police officers themselves. One of the great challenges currently facing traffic enforcement is to recognize that it is impossible to essentially improve traffic safety behavior by means of police forces alone and red light cameras serve as a deterrent against traffic violations. In addition considering the traffic system as whole, including the role and resources of the police, it is cleat that enforcement based on very high subjective detection probabilities only, will not be able to achieve even on a satisfactory level the compliance of all traffic rules. Overall the use of new technologies in traffic safety work in both assisting and controlling road user behavior also serves this purpose well. Every year traffic crashes kill the equivalent of a highly populated city and describe the deaths as accidents – something random and unavoidable. They are not accidents – they are collisions with a cause and effect – the causes are clearly defined in many countries crash data. More than 80% of identified contributing factors are either driver errors of commission or omission. Traffic safety literature shows that the decision-making of drivers in responding to the amber signal, especially for those caught in the dilemma zone, is governed by a multitude of traffic, situational, and behavioral factors. Enforcement measures, such as the operation of red light camera, also play a significant part in influencing the stopping propensity of drivers. Many studies have found that a large and highly significant reduction in red light violations several months after implementation of the red light camera enforcement program in USA, Canada, England, Scotland, and Singapore. (1) However, it is likely that effects of red light camera enforcement strategies in other countries may differ, depending on factors such as the number of cameras deployed and the extent of publicity about them. Public opinion surveys in European countries, where automated traffic enforcement has been in use for many years, revealed that the majority of drivers support or accept red light camera use. (2) Violation of traffic controls at signalized road junctions is one of the major safety problems in industrialized countries. While less than half of one percent of vehicles entering signalized intersections may actually commit red light violations (1, 3) the potential traffic safety consequences are more serious. In the most serious red-light running collisions, the vehicles hit each other at right angles. The resulting side-impact collisions cause severe injuries sometimes leading to death. More than 1 million motor vehicle crashes occur annually at traffic signals in US alone. (4) High compliance with signals is essential for safe and efficient traffic movement, and noncompliance contributes substantially to urban motor vehicle crashes. (5) Efforts to promote traffic law compliance are constrained by limited police enforcement resources, which have been declining in relation to the number of vehicles on the road. High compliance with signals is essential for safe and efficient traffic movement, and noncompliance contributes substantially to urban motor vehicle crashes. (5) Camera enforcement is intended to modify driver behavior through both general deterrence and punishment of individual violators. One recent international review of the literature on effectiveness of the red light camera shows that in overall, injury crashes, including rear-end collisions, were reduced by 25-30% as a result of camera enforcement. (1, 5) Retting and Kyrychenko (6) have emphasized that although red light cameras are effective in reducing red light violations and associated crashes, such enforcement should be viewed as a supplement to, and not a substitute for, good engineering design practices that can reduce red light running and enhance intersection safety. These practices include adequately timed yellow signal change intervals, use of all-red clearance intervals, conspicuous traffic signal housings, adequate signal brightness, coordinated signal timing, and use of advance warning signs on high-speed roads or at locations with limited sight distances. (6) We need more novel strategies to change attitudes and behaviors through evidence based education rather placing whole emphasis on enforcement to deter inappropriate driving behavior. Education should be integrated in to major component of the successful approach to red light running and it is to be done in concert with legislation and enforcement. Enforcement of traffic laws should be secondary to deterrence, as voluntary compliance should be promoted through evidence based educational campaigns that underlies the public health promotion approach for traffic safety. Health promotion is the companion process of enabling individuals and communities to increase their control over and improve their health and reduce injuries by promoting healthy life styles. Motor vehicle crash prevention must be seen in the broader context of public health, healthy public policy, and media portrayals of health and lifestyle choices. By improving the road infrastructure the need for enforcement could be considerably decreased. There are actually number of measures available that, when applied extensively could to a large extent substitutes enforcement. These include road humps small roundabouts more sophisticated traffic signal systems, and the introduction of in-vehicle/ infrastructure supported telematics system such as intelligent speed-limiters or alcohol interlocks. Sweden was the first country to introduce the zero-tolerance principal. This based on the ethical principal derived from road users’ abilities and needs. The transport system has been designed and constructed in such a way that all citizens are served and that a human error in traffic will not lead to severe injury. This principal means that the ultimate goal of traffic safety work is zero fatalities. Moreover zero tolerance means sharing the responsibility for safety. It means that the traffic police are still needed but that they can operate in an environment so designed that they can concentrate primarily on serious driver law violations and have a more educational role in traffic than present. References: (1).Retting, R.A.; Ferguson, S.A.; and Hakkert, A.S. 2003. Effects of red light cameras on violations and crashes: a review of the international literature. Traffic Injury Prevention 2003: 4(1): 17-23. (2). Muskaug. R., Drivers acceptance of automatic traffic surveillance. Traffic Engineering and Control, 1993; 34 243-246 (3).Kamyab, A., McDonald, T., Stribak, J., (2002) The scope and impact of red light running in Iowa. Presented at the 81st Annual Meeting of the Transpotation Research Board, Washington, DC. (4) US Department of Transportation, Washington,Traffic Safety Facts 1997 (HS-808-770). US Department of Transportation, Washington, DC. (5). Retting, R.A., Williams, A.F., Preusser, D.F. and Weinstein, H.B., Classifying urban crashes for countermeasure development. Accident Analysis and Prevention 1995; 27:283–294. (6). Retting, R.A. and Kyrychenko, S., Crash reductions associated with red light camera enforcement in Oxnard, California. American Journal of Public Health 2002;92(11): 1822-1825. Competing interests: None declared
Re: Automated traffic law enforcement 2 March 2005
Dr. Herbert H. Nehrlich, Private Practice Bribie Island, Australia 4507 Send response to journal: Re: Re: Automated traffic law enforcement	Beautiful province this place called British Columbia. I am sure there are a few red light cameras, strategically placed and I am equally sure that they regularly catch their offenders. Running red lights may involve speed, most often a sudden burst of speed, however, the lengthy comment from the Canadian Coast talks in great detail, and with much passion, about Red Light Cameras. They missed the subject altogether! There is a glaring difference between those and Speed Cameras and that, unless I missed something, was the subject so hotly debated. I won't comment on the new topic other than to say that the weakest argument sticking out like a red camera is the one about police not being able easily to follow red light runners because of the dangers to others and themselves. They could simply wait on the other side! I am looking forward to more on the speed cameras. Competing interests: None declared
A few responses... 2 March 2005
David Dorn, Freelance Journalist Durham DH4 Send response to journal: Re: A few responses...	What Ediriweera propounds is all well and good - but how does that relate to "Speed" cameras? In fact it doesn't. Peter Morrell syas: "The speed camera is just one more measure designed to slow traffic down" when, if he cares to do the research, it was designed by Mr Gatsonides to catch people exceeding an arbitrarily set speed. It was, in fact, designed as a fine-levying device. Then he goes on to say: "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? " One council local to me has had cause to regret its speed humps - in its attempt to build them high enough to get a maximum speed of 10mph (in a 30mph limit), they also achieved a situation where at least five models of car cannot get over them without body damage - at *any* speed. They've been forced to pick up the bill for the damage they've caused. Pelican crossings? Yes, fine - but not placed in stupid positions - like right beside a pedestrian underpass - a purpose-built tunnel for folks to use to cross the road in complete safety from traffic, because they're underneath it. Then the traffic planners decided to put in a Pelican. Lord knows why - I'm sure I don't. It now sits there, kids coming out of the tunnel and hitting the button at peak traffic times, causing immense hold-ups on the major roundabout which the tunnel serves, and causing crashes at very regular intervals. Very sensible - NOT! I have nothing against pedestrianisation, and making sensible use of roadways in heavily urban areas - in fact, cul-de-sacs in residential areas are a very good idea - but why does Peter think that the car "ruins our lives"? Iss he giving away his agenda? And finally, James Woodcock - how sad to see that he resorts to that epithet - "speedophile" a term coined by activists who delight upon its audible similarity to "paedophile" - let me just say this - if I see that word used, I know that whoever has used it will not be worth reading or listening to. Competing interests: None declared
Re: A few responses... 3 March 2005
James D Woodcock, Research Student London School of Hygiene and Tropical Medicine Send response to journal: Re: Re: A few responses...	In response to David Dorn who gets so upset about my use of the term speedophile. Perhaps he should consider why the harms of speeding could be compared with the harms of paedophilia? Traffic is a particular danger to children and speeding drivers kill and ruin the lives of 1000s of children every year in the UK alone, whilst restricting the safe play of hundreds of thousands more. Any resonance there? On his support for underpasses, I wonder if David Dorn spends much time in them? His favourable view is not shared by most pedestrians. Indeed they are great for cars, as they give them the streets, while forcing pedestrians into dark, smelly tunnels underground. Has he considered if many single women feel safe in underpasses? His argument shows clearly a certain strand of thought in ‘road safety’. This is that cars are entitled to the streets and the free movement of traffic must not be impeded. Therefore, as this right to dangerous behaviour is a given move everyone else out of the way, no matter the inconvenience for them. So to answer why cars ruin our lives, although the pro car/speed lobby appear incapable of considering car dependency from a public health perspective. In addition toroad traffic injuries, they steal space from pedestrians and cyclists- in particular in poorer, inner city areas. Busy roads sever communities. Cars kill through air pollution. They are the biggest cause of noise pollution. Road transport is the fastest growing contribution to climate change emissions. They promote sprawled living that destroys communities and denies access to amenities for non car owners. Oil production for motorvehicles is a major cause of environmental damage, war, civil war and corruption. Car production and use consumes vast amounts of resources and land that could be used for agriculture, recreation, health or other life promoting ends. Does this suggest to David why cars ruin our lives? Competing interests: None declared
In reply to James D Woodcock 4 March 2005
David Dorn, Freelance Journalist Durham DH4 Send response to journal: Re: In reply to James D Woodcock	James D Woodcock said: "In response to David Dorn who gets so upset about my use of the term speedophile. Perhaps he should consider why the harms of speeding could be compared with the harms of paedophilia? [...]Any resonance there? " In answer - no, none. The term has been coined spitefully and cynically - and should not be used by anyone seeking to be taken seriously. Next: On underpasses... Let me reiterate for JDW that the safest roads in the UK are motorways and non-urban dual carriageways. It is noticeable that pedestrians and cyclists are not allowed to use them. The "strand of thought" is that roads are inherently dangeorus, and that in a collison, a ten stone single woman is no match for a ton and a half of steel and aluminium. If JDW is seriously interested in reducing the casualty figures, then surely he must acknowledge that a degree of segregation of the two might just help? Or is he just anti-car? (as well as being anti- war) Perhaps his last paragraph more clearly demonmstrates his stance: "They steal space from pedestrians and cyclists" Pedestrians have the vast majority of the country to walk freely upon - successive regimes have pedestrianised more and more of our cities, releasing more and more space for pedestrians and cyclists. "Cars kill through air pollution. " Buses and trains emit much more pollution than cars "They are the biggest cause of noise pollution. " Depends where you live - in my neck of the woods, crows cause more noise. "Road transport is the fastest growing contribution to climate change emissions. " Or, depending on what you read, the most controlled and decreasing emitter of CO2 "They promote sprawled living that destroys communities and denies access to amenities for non car owners. " No - people do that of their own accord because they don't want to live in cities. "Oil production for motorvehicles is a major cause of environmental damage, war, civil war and corruption. " Sounds like propaganda to me "Car production and use consumes vast amounts of resources and land that could be used for agriculture, recreation, health or other life promoting ends. " and more propaganda - but in my neck of the woods is a major provider of jobs. And JDW may well notice that agriculture in this country doesn't suffer from land being filched from farmers. "Does this suggest to David why cars ruin our lives? " No, but it does suggest that you are anti-car, and, if I read you correctly, anti a lot of other things, too - indeed, that you're probably an activist of sorts. However, none of that gives you - or anyone else - the right to try to equate car drivers witrh child molesters. None of it. Competing interests: None declared
Re: In reply to James D Woodcock 10 March 2005
James D Woodcock, Research Student LSHTM Send response to journal: Re: Re: In reply to James D Woodcock	In response to David Dorn who appears concerned what I am anti. Let me clarify I am pro public health, equity, access, and environmental sustainability. The question I ask is how the car and truck as means of mass people and goods transport fit with those ends. In detail: On underpasses he said “Let me reiterate for JDW that the safest roads in the UK are motorways and non-urban dual carriageways. It is noticeable that pedestrians and cyclists are not allowed to use them. The "strand of thought" is that roads are inherently dangeorus, and that in a collison, a ten stone single woman is no match for a ton and a half of steel and aluminium. If JDW is seriously interested in reducing the casualty figures, then surely he must acknowledge that a degree of segregation of the two might just help? Or is he just anti-car? (as well as being anti- war)” It is not roads that are inherently dangerous but vehicle traffic, particularly when moving fast. The question is; who has the right to be there? Motorways may be relatively safe but where does traffic go when it comes off these safe motorways, except into towns and cities where people live. Of course as I said before once you have established the right of cars and trucks to speed through streets where people live the only safe option is to stop people using those roads. However, this also stops them playing and exercising and often reaching amenities. “Pedestrians have the vast majority of the country to walk freely upon - successive regimes have pedestrianised more and more of our cities, releasing more and more space for pedestrians and cyclists.” Successive regimes have built more and roads for cars. After a hiatus following the protests of the 1990s the UK government is once again building new roads. Across Europe every day another 10 hectares (10,000m2) of land is covered by new roads according to EU figures. Dorn should also remember that pedestrian areas are not usually suitable for cyclists. In most cities only a very small area is pedestrianised, and usually in the tourist centre not where people live. It is also not meaningful to say we have the vast majority of the country to walk freely upon. Firstly, people need space near where they live and to be able to get there safely. Secondly despite new access rights we have only limited rights of way over the majority of rural Britain. Previously I said, Cars kill through air pollution, he replied “Buses and trains emit much more pollution than cars” This issue can be considered from two perspectives. The pollution per passenger mile of different modes of transport or the total pollution from a car dominated compared with a public transport dominated system. Clearly electric trams, trains and cars, and walking and cycling do not produce much in the way of local air pollution, which is what produces produces the vast majority of pollution deaths now as opposed to future climate change deaths. However, while electric subways and trams are commonplace, electric cars are still very rare. Diesel buses were often introduced (particularly in USA but also UK) after car/oil interests managed to destroy far more efficient electric trams. However, diesel buses still do not usually produce more harm through pollution per passenger km than cars. Cars also create far more congestion than buses thereby reducing the fuel efficiency of buses as well as the cars. For electric transport systems the pollution (not counting the pollution to produce them) depends how the electricity is generated. If this is non polluting renewable energy then no problem. However, unfortunately it is more likely to be fossil fuels or nuclear. The pollution contribution therefore depends on the efficiency of the transport mode. For urban travel the efficiency of a transport system depends on the vehicle occupancy and the compactness of the city. Apart from where vehicle occupancy is very low buses are more energy efficient than cars (trains and trams even more so). Comparing cities with high public transport versus high car use the figures are much more striking because of the higher efficiency of public transport when it is a mass system and because of the sprawled nature of the more car dependent cities.[1] My guess is David Dorn may have reached his conclusion having seen a report on the much quoted (and misrepresented) research by Roger Kemp published last year on rail fuel efficiency between London and Edinburgh. He estimated that a 225kmph train might be as fuel inefficient as a much slower car given the same occupancy percentage (a very fast 350 kmph train would be less efficient).[2] Firstly, this is comparing high speed trains (225 kmph) with slower speed cars (and a particularly fuel efficient car at that). Secondly, Kemp recognises this is largely a result of the rolling stock development in the UK after privatisation and the narrow UK gauge and not of trains per se. Figures from a parliamentary question in 2004 estimate that currently trains on this route were 6 times more efficient than cars, based on estimated current occupancy rather than assuming equal occupancy ones (interestingly coaches were more efficient still). Thirdly, these figures do not apply to urban commuter transport, for which Kemp agrees rail is far more fuel efficient. And fourthly it does not include the greater emissions for cars in congested traffic when arriving or leaving the city. Also most importantly it is not relevant to the majority of air pollution deaths from local air pollution. Certainly none of this disproves in the slightest that cars and trucks kill through air pollution. Kunzli 2000 found that for Austria, France and Switzerland 40,000 deaths per year are attributable to air pollution, about half specifically to traffic pollution.[3] From a public health perspective the most obvious solution is to firstly promote the least polluting transport modes (walking and cycling). Secondly to halt or reverse the ever increasing distances travelled by people and goods, (which is primarily by car and truck) by promoting local production and local access to jobs, shops, leisure and services. And thirdly to provide electric urban transport from renewable sources. I said "They are the biggest cause of noise pollution. " he replied "Depends where you live - in my neck of the woods, crows cause more noise." Most people in this country live in cities in which car transport is the biggest cause of noise, although increasingly, road freight causes noise problems for people in both town and country. However, the rural car driver bothered by crows will often drive to work in the city so imposing the noise pollution from their car on the city dweller. I said "Road transport is the fastest growing contribution to climate change emissions. " he replied "Or, depending on what you read, the most controlled and decreasing emitter of CO2" Please could you tell me what you read? I read the IPCC and the International Energy Agency reports. To quote from a 2004 IEA report, “In 2000, transport accounted for about 5 gigatonnes of CO2 emissions worldwide, or 21% of total energy-related emissions. By 2030, transport CO2 is projected to rise by 87% to 9 gigatonnes, or a 24% share of the total. And that is only CO2 coming directly from vehicles. Including “upstream” emissions (CO2 released during fuel production and delivery to vehicles) transport’s share is closer to 28%.”[4] He said "No - people do that of their own accord because they don't want to live in cities." Why don’t people want to live in cities? The biggest reason cities are unpleasant is the danger, pollution and noise from cars. In the USA historically we also need to consider racism and government subsidies of mortgages. Cars consume much more space then other transport systems, to park and to drive, so more cars make the same population density feel more cramped. Of course as people move out to escape the problems of the car many of these are then recreated in the suburbs but leaving the city centre dwellers further and further from the countryside. I said "Oil production for motorvehicles is a major cause of environmental damage, war, civil war and corruption. " he replied "Sounds like propaganda to me" The statistical association between primary commodity production (particularly oil) and war, corruption, low economic growth, and poverty is well documented by social scientists from across the political spectrum, who provide a range of theoretical explanations for so called ‘Dutch disease’. I refer you to the Christian Aid report, which references some of the primary literature.[5] "Car production and use consumes vast amounts of resources and land that could be used for agriculture, recreation, health or other life promoting ends. " he replied, "and more propaganda - but in my neck of the woods is a major provider of jobs. And JDW may well notice that agriculture in this country doesn't suffer from land being filched from farmers." Of course saying it provides jobs is another way of saying it uses resources, which could be used for other things. The same could be said of arms and tobacco. The question from a health perspective is whether the labour (and high capital invested) could be better used elsewhere. I assume he also realises the UK is increasingly dependent on imported food and this movement of food is itself a major contribution to pollution. Of interest it is estimated that if China currently motorising rapidly achieved Japan’s level of car ownership per capita it would require 13 million hectares of land, most of which would be cropland.[6] This is over half of China’s current rice cropland. If Dorn wishes to reply I hope he can provide some evidence to support his assertions and not just accuse me of propaganda. [1] Newman P, Kenworthy J. Cities and sustainability: overcoming automobile dependence. Washington, DC: Island Press, 2000. [2] http://www.engineering.lancs.ac.uk/Userfiles/Publications/Transport%20Energy%20 Consumption%20Discussion%20Paper.pdf [3] Kunzli N, et al.Public-health impact of outdoor and traffic- related air pollution: a European assessment. Lancet, 2000, 356:795-801 [4] IEA/EET working paper Reducing oil in transport. Lew Fulton. www.iea.org/textbase/papers/2004/transporthree.pdf [5] Christian Aid: Fuelling poverty. Oil, war and corruption http://www.christian-aid.org.uk/indepth/0305cawreport/cawreport03.pdf [6] Whitelegg J and Haq G. World Transport policy and practice. Earthscan 2003 Competing interests: None declared
Woodcock and Dorn... 11 March 2005
David Dorn, Freelance Journalist Durham DH4 Send response to journal: Re: Woodcock and Dorn...	Woodcock says: "If Dorn wishes to reply I hope he can provide some evidence to support his assertions and not just accuse me of propaganda. " Dorn has no wish to reply. He considers that Woodcock's citations and rhetoric amply demonstrate exactly where he is coming from, and it is obvious that, no matter what Dorn cites as evidence, Woodcock will find yet more propaganda to uphold his assertions. What Woodcock fails to appreciate, however, is that Dorn maintains a balanced view - or at least tries to. In that regard, Dorn places Jobs above recreation and applauds attempts to decrease greenhouse gas emissions from vehicles (a process all manufacturers are undergoing, to the extent that, now, the exhaust gasses are cleaner than the air being drawn into the engine). However, Woodcock has amply demonstrated why his support for Speed Cameras is so all-encompassing - and it has nothing whatever to do with speed reduction, but vehicle number reduction. Competing interests: None declared
Please keep it factual and on track 18 April 2005
Robert A Brookbanks, IT consultant Self Employed PE4 7RY Send response to journal: Re: Please keep it factual and on track	I read this debate with interest. I know speed cameras are an emotive issue, and that can be witnessed as this discussion has escalated. I believe the original paper was trying to assess if speed cameras are an effective safety device. Perhaps an alternative paper looking at the other side of the coin would balance out the arguement, to wit; have speed cameras inadvertently casued an increase in road deaths and serious injuries? I have noticed that despite an increasing number of cameras, KSI statistics are up. We have had cameras for over a decade and they appear to have failed quite catastrophically. Please try and focus on the cost in human life and injury that the cameras may have caused. Without proper randomised studies to get to the truth, the camera could be a silent killer in our midst. I would be interested in the comments from anyone in the frontline in A&E who has any observations. Competing interests: Programmer in a study to gather statistical data to assess the impact of differing treatment methods in trauma injury.
confounding factors 2 May 2005
James B Norwood, physician Reno, NV 89513 Send response to journal: Re: confounding factors	The authors of this article mentioned the possibility of "confounding factors" affecting the apparent results of their analysis. I would like to suggest that there is a significant confounding factor in all the studies done on this subject. By way of doing so, let me relate a story. While a medical resident, I commuted over a distance of 12 miles by bicycle and on weekends went on long recreational rides in the country. Once, I was asked by someone who saw me on a very convoluted, forested country lane why I would ride in such a dangerous area. I pointed out that I was never endangered on that road by a car because the drivers perceived that it was a dangerous road and were extremely alert. Therefore, they always saw me and avoided me. Conversely, I was struck by cars on two occasions (one car struck me three times without the driver becoming aware of me) on a broad avenue with two traffic lanes and a full width shoulder in each direction. In all cases I was well onto the shoulder and "sideswiped" (fortunately without injury) as the car came onto the shoulder. My conclusion was that the driver's state of alertness and traffic awareness was the key factor in avoiding a collision. People driving on a wide, straight road tend not to pay much attention and use their spare attention to drink, eat, shave, and converse on the phone with their friends. Since that time, this conclusion has been reinforced many times. I would submit that the knowledge of being observed by "the law" heightens awareness and results in fewer collisions. The camera is simply the device that causes this phenomenon. I suspect that a policeman on foot at the roadside with a bullhorn admonishing drivers to pay attention to their surroundings would have the same effect at considerably less expense. Of course, it would fail to produce the revenues the cameras do, which would handicap the idea in the minds of both British and american politicos. Competing interests: None declared