The case against bicycle helmet advocacy: a quick guide

Bicycle helmets are tested with vertical drops from a maximum height of about 3m onto flat surfaces (BS/EN 1078:1997). In such testing, helmets definitely help. However, the scientific evidence on helmets & population wide injury rates is far from clear that helmets actually are beneficial.

While amongst cyclists who suffer injury, helmets of themselves do reduce head injuries significantly, they also increase neck and facial injuries, so that there appears to be negligible benefit overall (Accident Analysis & Prevention: … meta-analysis of bicycle helmet efficacy). Study of bicycle injury rates in Australia around the time of introduction of mandatory helmet laws suggests that, though there is a noticeable dip in injury rates around the introduction of the law itself (not necessarily attributable to the helmet itself in my opinion) that injury rates then started increasing again, to the point rates were nearly the same at the end of the study period as before the helmet law, and trending to surpass it! (My Blog: study-shows-australian-cyclist-helmet-law-leads-to-increasing-head-injury-rates). Helmet use also appears to induce risk-compensation behaviour in motor vehicle drivers – they make closer passes (Accident Analysis & Prevention: Drivers overtaking bicyclists…). No doubt the cyclists themselves also are subject to risk compensation. Thus, by wearing a helmet there may be an increased risk of getting into an accident.

There may be further population wide psychological effects caused by a culture of “Must be wearing a helmet to be safe!”. It is sending the message that cycling needs safety equipment, and hence must be dangerous, which surely will put off many – certainly where mandatory helmet use laws are introduced rates of cycling then significantly decrease. The reverse is of course true: the overall health benefits of cycling greatly outweigh the quite tiny risks – risks which are not greatly changed by helmet wearing, the studies appear to say. In other words, by advocating helmet use, one may be harming the rates of cycling by sending the wrong message on safety, and hence harming public health overall.

Further, as cyclist safety on the roads correlates strongly with rates of cycling – more cyclists leads to more awareness & safer roads, and similarly fewer cyclists means less safe roads – this means a culture of helmet use may well lead to increased injury rates amongst cyclists (in addition to the general adverse public health effects of fewer people cycling). This would be very hard to categorically prove or disprove in causal terms, however the Australian experience certainly suggests a correlation, as I think would a comparison of the UK and Netherlands.

Finally, in the Netherlands, one of the safest places for cycling in the world, cyclists almost universally do not wear helmets, including very young cyclists. Thus, we can be quite certain that helmet usage is not a pre-requisite for safe cycling. Indeed, it is in places like the UK and USA, with some of the worst cycling safety in the developed world, where the focus on safety equipment for the cyclist seems to be greatest.

In short, the focus needs to be on those things around the cyclist (e.g. default legal liability to influence motorists’ behaviour, safer road infrastructure, etc) – not what is on cyclists. Focusing on cyclist safety equipment to me seems futile at best, and perhaps even detrimental to the cause of mass, safe cycling, if that’s a cause you believe worthwhile.

NB: Helmet use should always be a personal choice. The issue is complex, the trade-offs may differ greatly in different scenarios – helmets may be very beneficial in some settings, e.g. some kinds of racing. The choice should be your own. However, general advocacy of cycling helmets seems inappropriate and probably harmful, to me.

18 Comments »

  1. Tim Beadle said

    There may be further population wide psychological effects caused by a culture of “Must be wearing a helmet to be safe!”. It is sending the message that cycling needs safety equipment, and hence must be dangerous, which surely will put off many

    The BBC’s insistence that anyone cycling on TV (certainly on kids’ TV) be wearing a helmet is a massive example of this “dangerisation” of cycling. The worst example I’ve seen is the CBeebies show “Same Smile” where the presenter, riding a cargo trike at about 4mph, is seen wearing a helmet. Utterly bonkers, and detrimental to the cause of getting more people cycling.

    • Paul Jakma said

      Madness indeed. Presumably if they were seated, their head was lower than if they were upright. So, if they were going at walking pace on the trike, then their head was at *decreased* risk of injury relative to walking. In other words, the BBC ought to also make this presenter wear a helmet while walking! ;)

      • Richard Burton said

        The BBC is engaged in a campaign to promote cycle helmets, and has been doing so for over twenty years. They have a Charter which is very specific about impartiality and bias, but every programme that I am aware of has been blatantly, undeniably partial and biased. Despite many complaints and being provided with overwhelming evidence, the BBC deny any bias.

        The latest was The One Show broadcast in the spring, which gave three times as much time to helmet proponents as sceptics and interviewed James Cracknell, who claimed that his helmet saved his life, without pointing out that he is sponsored by the helmet manufacturer. According to the BBC this is impartial and isn’t bias.

  2. Kim said

    I think you will find that the worst cycling safety in the developed world is actually Australia and New Zealand, oh and they have compulsory cycle helmets for everyone.

    • seamus gardiner said

      probably why they need to wear helmets then….

  3. Paul Jakma said

    Another interesting study here: http://bit.ly/uogrwR – which appears to confirm the Sheffield study in that gender & appearance of the cyclist affect the behaviour of motorists in how close they pass.

  4. Paul Jakma said

    The paper concerned is also discussed here: http://theconversation.edu.au/putting-a-lid-on-the-debate-mandatory-helmet-laws-reduce-head-injuries-1979 with interesting debate in the comments section, including from the authors.

  5. Paul Jakma said

    Another study showing helmet laws do reduce cycling head injuries in children. However, it is accompanied by increase in head injuries in children from other causes, suggesting that the cycling decrease is due to drop in cycling rates rather than the effect of the helmets on crashes:

    http://www.nber.org/papers/w18773

  6. Paul Jakma said

    Helmet wearers cycle more slowly if made to cycle without: http://www.sciencedirect.com/science/article/pii/S0001457512001169

  7. Paul Jakma said

    Study of New Zealand helmet laws suggests a negative impact on mortality, due to the significant decrease in cycling post-law:


    The New Zealand helmet law (all ages) came into effect on 1 January 1994. It followed Australian helmet laws, introduced in 1990–1992. Pre-law (in 1990) cyclist deaths were nearly a quarter of pedestrians in number, but in 2006–09, the equivalent figure was near to 50% when adjusted for changes to hours cycled and walked. From 1988–91 to 2003–07, cyclists’ overall injury rate per hour increased by 20%. Dr Hillman, from the UK’s Policy Studies Institute, calculated that life years gained by cycling outweighed life years lost in accidents by 20 times. For the period 1989–1990 to 2006–2009, New Zealand survey data showed that average hours cycled per person reduced by 51%. This evaluation finds the helmet law has failed in aspects of promoting cycling, safety, health, accident compensation, environmental issues and civil liberties.

  8. Paul Jakma said

    The paper “The Health Impact of Mandatory Bicycle Helmet Laws
    tries to mathematically model aspects of the net health benefits of cycling relative to the negative impacts on cycling participation of mandatory helmets laws. It finds that generally such laws lead to a significant *negative* effect on overall health:

    This article seeks to answer the question whether mandatory bicycle helmet laws deliver a net societal health benefit. The question is addressed using a simple model. The model recognizes a single health benefit—reduced head injuries—and a single health cost—increased morbidity due to foregone exercise from reduced cycling. Using estimates suggested in the literature on the effectiveness of helmets, the health benefits of cycling, head injury rates, and reductions in cycling leads to the following conclusions. In jurisdictions where cycling is safe, a helmet law is likely to have a large unintended negative health impact. In jurisdictions where cycling is relatively unsafe, helmets will do little to make it safer and a helmet law, under relatively extreme assumptions, may make a small positive contribution to net societal health. The model serves to focus the mandatory bicycle helmet law debate on overall health.

  9. Paul Jakma said

    Canadian study published in the BMJ, “Helmet legislation and admissions to hospital for cycling related head injuries in Canadian provinces and territories: interrupted time series analysis”, finds helmet law legislation has had a minimal effect on hospital admissions for cyclist head injuries:

    Reductions in the rates of admissions to hospital for cycling related head injuries were greater in provinces with helmet legislation, but injury rates were already decreasing before the implementation of legislation and the rate of decline was not appreciably altered on introduction of legislation. While helmets reduce the risk of head injuries and we encourage their use, in the Canadian context of existing safety campaigns, improvements to the cycling infrastructure, and the passive uptake of helmets, the incremental contribution of provincial helmet legislation to reduce hospital admissions for head injuries seems to have been minimal.

  10. Paul Jakma said

    BMJ editorial piece, by Ben Goldacre and David Spiegelhalter, on the risks of cycling and the net effect of helmet promotion on public health, “Bicycle helmets and the law” has an overview of the issues, and good references.

  11. Paul Jakma said

    The Vine magazine in Australia, with a good overview of the public health issues of helmet laws and the scientific evidence, inc links.

  12. Paul Jakma said

    An interesting overview of the data and research on the effect of mandatory helmet law in Alberta, Canada:

    “When changes in cycle use are taken into account, Alberta’s helmet law seems to have increased the risk of both head and non-head injuries.”

  13. Paul Jakma said

    Very good quantitative article on the effect of helmet law introduction in New Zealand on injury and participation rates. In a nutshell, participation dropped dramatically amongst all age groups while injury rates increases.

  14. Paul Jakma said

    Blog commenting on the impact of the New Zealand helmet law, which appears to led to reduced cycling (as in AU), and increased risk to the remaining cyclists. Links to (partisan) websites with further data.

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