Helmet laws hit the headlines - again

The public debate about mandatory helmet wearing laws in Australia has raged since Sue Abbott won an appeal to the District Court last August defending her failure to wear a helmet. Since then media coverage on the matter has been generally poor, often confusing the effectiveness of helmets in reducing head injuries following a fall, with the net social benefits of the law itself.

The debate

The debate is about mandatory helmet laws (MHL). The pro-choice side advocates repealing the law so that helmet wearing is voluntary (not compulsory non-helmet wearing as some mistakenly believe).

The argument is about whether the law itself provides net social benefits – not about whether an individual rider involved in a fall is more or less likely to injure their head by wearing a helmet. Evidence points to the fact that yes, a falling rider with a helmet will, on average, suffer less severe head injuries than a bareheaded rider.

But is this a justification for a law?

Not at all. You see wearing a helmet while walking and driving will also prevent head injuries in the case of an accident. But one side of the debate seems happy to leave these other activities alone, even though it fits logically with their argument. 

Health Costs

Indeed, supporters of MHLs often cite taxpayer-funded public health care as a justification. Yet this makes no sense whatsoever for the MHL debate, the tobacco taxes, or any other preventative health care issue.

As I have said before 

…that increasing preventative health care, while having the benefits of a healthier and long life, often come at increased total lifetime health costs, rather than decreased costs as is often proposed. Remember, we all die some day, and any potential cause of death postponed will allow another to take its place, which of course has its own health costs.

Alternatively, a more healthy existence may make us more productive for longer and lead to us contributing more in taxes over our lifetime than the potential increase in health costs which were paid through the tax system for our preventative care.

Governments, and subsequently economists, worry about these things because many health care costs are borne by others though tax revenue, yet the net economic effect is anything but straightforward.

The arguments 

The only argument remaining in favour of MHLs is that we are saving people from themselves. It is a pretty weak argument for making law in my view.

The pro-choice advocates usually cite a variety of factors to demonstrate that any benefits an individual may receive by wearing a helmet can be significantly offset by their own risk compensation and the changes to the behaviour of other road users.

For example

1. Drivers will pass helmeted cyclists closer than bare headed cyclists (with cyclists with long blonde hair getting the most room).
2. Helmets make cyclists feel safer, and they adjust by taking more risks (risk compensation) 
3. Helmet laws decrease the number of cyclists on the road, making car drivers less familiar with cyclist behaviour and making each remaining cyclist less safe.
4. Helmets increase diffuse axonal injuries of the brain and neck due to their increased diameter (and increased the likelihood of impacts due to the larger volume). As Sue Abbott argued in her court case – a helmet can increase angular acceleration which an oblique impulse imparts to the head, increasing the risk of damage to the brain, especially diffuse axonal injury 
5. Helmets can be a hazard in many circumstances (with many child deaths recorded as a result of helmet wearing) 
6. Any deterrent to cycling is likely to increase time spent on sedentary activities, further contributing to the obesity epidemic. 
7. The law allows governments to appear to be acting in the interests of cyclist safety, while neglecting other measures to improve cyclist safety, such as bike lanes or driver education.

Added together, mandatory helmet laws are not a clear winner on any social benefit measure. 

Missing the point

Most media commentary has missed the point of the debate. The pro-choice side does not argue that helmets are worthless for any individual rider if they are to hit their head. They simply claim that helmets are not as effective at reducing injuries as they are made out to be and the many flow-on social effects that further reduce cyclist safety are not considered.

Even academics have a hard time finding strong evidence that helmet laws have reduced head injuries significantly. The Voukelatos and Rissel paper I referenced in a previous post, showed evidence that the benefits of helmet laws in reducing the ratio of head to arm injuries for hospitalized cyclists was insignificant compared to other road safety improvements in the late 1980s and early 1990s. It was later retracted after criticism over data inaccuracies (corrected data in the graph below), with the critics now publishing their own study using similar statistics to examine the effect of the law in NSW. They find that there is a statistically significant impact of the law in reducing the ratio of head to arm and leg injuries.

Unfortunately, their model also found that the helmet law led to fewer hospitalisations of pedestrians with arm injuries.

For cyclists who do fall in a manner leading to significant injuries, a helmet may reduce head injuries. That it is so difficult to see the effect of helmet laws in the data suggests that any benefits of helmet wearing must be very small, even at an individual level. MHL supporters usually feel that helmets prevent almost all head injuries. But this is not the case. They at best provide a marginal improvement in head safety.

I hope this brings a bit of perspective to the issue for readers who stumble across helmet headlines.