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LETTERS: Barry Pless and Ron Davis Cyclists should wear helmets BMJ 1997; 314: 977 [Full text]

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Reality is the highest authority

Malcolm J Wardlaw   (12 February 2007)

Reality is the highest authority 12 February 2007
Malcolm J Wardlaw, Design Engineer n/a Send response to journal: Re: Reality is the highest authority	A recent Injury Prevention editorial [1] criticised opposition to cycle helmet legislation. The Editor argued that cycling is a dangerous activity and that legislation to compel helmet use has been effective to reduce the incidence of serious head injuries. XX Despite the long tradition of helmet promotion, the actual risk in cycling was rarely studied until recently. The only known (thorough) risk assessment by an official agency was “Risk in Cycling” [2] by the British Transport Research Laboratory. This was completed in 1987, but was never published. It reported, inter alia, that in Britain pedestrians faced higher risks per per mile than cyclists and that cyclists and drivers faced similar long-term risks. XX The writer obtained a copy of this report about five years ago. He carried out a broader study of risk [3] that confirmed the TRL findings, and added further results. It confirmed the now widely remarked effect that risk in cycling falls when the number of cyclists increases, although reduced cycling tends to increase risk. XX A particularly interesting finding concerned cycling as a means to reduce road deaths. In Britain, the driver safety record is excellent, while most cyclists are boys and young men, and the level of cycle use is low. Consequently the average risk (per hour) is 2-4 times higher than for drivers. This does not mean discouraging cycling would reduce road deaths. Cyclists almost never kill third parties. Drivers kill approx. 1,100 third parties every year in Britain. When these deaths are taken into account, it turns out that even in Britain, cycling is hour for hour less likely to add to road deaths overall than driving. In other industrialised countries, cycling will be reducing road deaths more clearly, since the driver safety record is generally poorer and the cyclist safety record generally better. Similarly, a renaissance of cycling in Britain would most likely reduce risk to cyclists and to third parties. XX A further study [4] by a Danish researcher has confirmed many of these results. XX One could only begin to consider helmet compulsion if cycling actually were dangerous. However, it is not, it is merely believed to be. Cycling for the ordinary trips of life incurs everyday risks. Public policy and competent professional opinion ought to respect this. XX The advantages of a revival in mass cycle use extend beyond improving cyclists' and non-cyclists' safety. In 2004, the British Commons Health Committee released a report on the obesity crisis in which it concluded: “ If the government were to achieve its target of trebling cycle use in the period 2000-2010, that might achieve more in the fight against obesity than any other individual measure”. Studies [5] show that moderate levels of cycling – as little as 20 minutes per day – can materially reduce mortality. XX Doubts persist as to whether enforced helmet legislation suppresses cycling levels. It has been consistently documented that enforcement is followed by enduring falls in the number of cyclists [6]. Interestingly, a recent study [7] by the National Institute for Clinical Excellence reported that the promotion of cycling led to falls in cycle use. Might this be because the promotional efforts were actually helmet programmes in disguise? XX It has been demonstrated [8] that large increases in helmet use accompanying enforcement did not affect serious injury trends. Interventions yield a discernible effect if they are effective. If an intervention consistently fails to yield an improvement, inquiry should focus upon the reliability of the original research. It is no secret that case-control studies usually report effects that later turn out to be exaggerated or wrong [9]. With helmets as in any other inquiry, reality is the highest authority; it is what actually happens that counts. XX In a previous eLetter [10] to the Editor, the writer emphasised his concern that a paper [11] published by Injury Prevention in 2001 had not made a complete presentation of evidence. Its authors concluded that helmet legislation had not deterred cycling by Ontario children. This paper was the primary factor in the British Medical Association's move to support an all-ages helmet law, having previously been against helmet compulsion due to the consequent deterrence of cycling. XX The Ontario law was never enforced, but this was not reported by the authors in their 2001 Injury Prevention paper. This created the risk that their conclusions could be misinterpreted to apply to enforced legislation, since reporting the effects of unenforced legislation would appear too trite for publication. The BMA was at pains to emphasise in its policy paper that it was calling for enforced legislation. The authors are now encouraged to publish an open letter to the BMA confirming that the Ontario child cyclist helmet law was never enforced, so it would not be safe to apply its results to an enforced law. XX In view of the extensive benefits of a revival in cycling, it is peculiar that there is not more concern at the stagnation or decline of cycling in all industrialised countries. 75% of car trips are short enough to make cycling a possible alternative mode. Addressing obesity, lack of physical exercise, car dependency, perceived danger in suburban streets and traffic congestion are all reliant on a major elevation of the status and use of the bicycle. This could happen if cycling was recognised as a healthy, low-risk and accessible form of daily transport. XX References XX 1. Pless B. Are Editors free from bias? A special case of Letters to the Editor. Injury Prevention 2006;12:353-354. X 2. Morgan JM. “Risk in Cycling”. Transport Research Laboratory Working Paper WP/RS/75 TRL Crowthorne, 1988. X 3. Wardlaw M. Assessing the actual risks faced by cyclists. Traffic Engineering and Control 2002;43:420-24. X 4. Krag T. “Cycling, safety and health”. www.ecf.com/publications/Download/050113_Cyling_safety_ecf_Thomas%20Krag.pdf X 5. Rutter H. Transport and public health fact sheet. www.modalshift.org/presentations/fphmasm02/southportposter.pdf X 6. “Helmet laws: what has been their effect?” Bicycle Helmet Research Foundation. http://www.cyclehelmets.org/mf.html?1096 X 7. “Transport interventions promoting safe walking and cycling.” The National Institute for Clinical Excellence, 2006. http://www.nice.org.uk/page.aspx?o=346196 X 8. Robinson DL, No clear evidence from countries that have enforced the wearing of helmets. BMJ 2006;332:722-25. X 9. Ioannidis JPA. Contradicted and initially stronger effects in highly cited clinical research. JAMA 2005;294:218-228. X 10. “Timely release of information is important”. eLetter response by M. Wardlaw to Injury Prevention Nov 2006. http://ip.bmj.com/cgi/eletters/12/4/231#1600 X 11. Macpherson A, Parkin P, To T. Mandatory helmet legislation and children's exposure to cycling. Injury Prevention 2001;7:228-30. Competing interests: None declared