Bicycle Helmets

Mandatory bicycle helmets: does correlation mean causation?

Posted: November 1, 2011 | Author: Alan Davies | Filed under: Cycling | Tags: , , , , , |3 Comments »

Percent of total trips by bicycle (data from Pucher & Buehler, 2008)

It’s evident from the response to my article two weeks ago (Is the mandatory helmet debate a distraction?), that some people still see compulsory helmets as one of the major obstacles, perhaps even the main obstacle, to significantly higher uptake of cycling in Australia. So I want to look at the main arguments for repealing the compulsory helmet law.

As I’ve said before, I accept that mandating helmets in the early 90s was arguable policy, at least in the case of adults. If it were proposed for the first time today, I doubt it would get up (except for children). So I don’t think those who advocate repeal are necessarily “wrong”.

But in my view the helmet law is not the main thing holding cycling back in this country – it doesn’t even come close. And since it’s got virtually no traction politically, it’s also a waste of energy. Ultimately it distracts from the key issue – the danger, whether perceived or real, of cycling in traffic.

A key argument made by many repeal advocates is that countries without mandatory helmet laws have high bicycle use. Australia, in contrast, has both low mode share and draconian helmet laws; ipso facto, they say, mandatory helmet laws are the key problem.

What I think is happening here is the familiar problem of confusing correlation with causation.

There’s no doubt bicycle use in Australia is indeed low compared to some other countries. For example, according to Pucher and Buehler in Making cycling irresistible: lessons from the Netherlands, Denmark and Germany, bicycles capture 27% of all trips in the Netherlands and 18% in Denmark, but a mere 1% in Australia (see exhibit). And there’s no doubt helmets aren’t considered important in these countries – in the Netherlands, for example, less than 1% of adults and only 3-5% of children choose to wear a helmet when cycling.

But does the law on helmets explain why cycling is so much more popular in these countries than it is in Australia?

The first thing the repeal advocates should ask themselves is this: why are only 1% of trips in the UK taken by bicycle even though helmets aren’t mandatory in that country? That’s no better than here! Or why is cycling’s mode share only slightly better in Ireland and Canada than it is in Australia, even though these two countries don’t have mandatory helmet laws? Clearly, whatever the explanation is for the comparatively low rates of cycling in these countries, it has nothing to do with any compulsion to wear a helmet.

They should also ask themselves why there are such enormous differences between countries where helmets aren’t mandatory. The fact that bicycle use is more than twice as high in the Netherlands as it is in Germany – and nine times higher than it is in France and Italy – suggests pretty clearly that there are other highly influential factors affecting the propensity to cycle that have absolutely nothing to do with helmets.

Helmet policy doesn’t explain why bicycles capture 34% of trips in Munster, but 13% in Munich. Or why the corresponding figure for Groningen is 37% compared to 10% in Heerlen; or 20% in Bruges but 5% in Brussells; or 19% in Salzburg but 3% in Wien.

Rather than focussing so much on helmet laws, repeal advocates would do well to look at the differences in cycling infrastructure and regulation –  and hence in safety – between Australia and Europe’s top performing countries. They should note that Copenhagen, for example, has an impressive 400 km of completely segregated bike lane, even though it’s much smaller than Melbourne. And Berlin has 860 km of completely segregated bike lane. They should also look at factors like 30 km/hr speed limits in residential areas in some countries and the strong cultural and legal onus on drivers to respect cyclists.

Pucher and Buehler argue the key reasons cycling is so successful in Dutch, Danish, and German cities relative to other places (not just Australia) is down to extensive systems of separate cycling facilities, intersection modifications & priority traffic signals, traffic calming, bike parking, coordination with public transport, traffic education & training, and sympathetic traffic laws. They also point to the positive way cycling is promoted in these countries.

It’s no wonder people cycle more in Copenhagen and Berlin than in Melbourne and Sydney. And it’s no wonder they don’t bother to wear helmets – it’s much less dangerous!  Yet even so, Danish and German authorities extensively promote wider helmet use, especially by children.

Put another way, the reason Dutch, Danish and German cities have high levels of cycling isn’t because riders aren’t compelled to wear helmets. Rather, riders don’t wear helmets because they’re not necessary. And they’re not necessary because cycling’s an order of magnitude safer than it is in Australia, thanks to the myriad infrastructure initiatives and supportive policies like those identified by Pucher and Buehler.

Repeal advocates invariably fall back on the argument that cycling use collapsed in Australia when mandatory helmet laws were introduced in the early 90s. There was indeed a collapse – bicycle use by 12-17 year olds fell 44%. However, cycling by 5-11 year olds fell by a more modest 10% and cycling by adults actually increased (doubling in metropolitan Melbourne)!

In any event, that was 20 years ago – that cohort of young teens moved on long ago, taking their ideas of what’s “cool” with them. Since then cycling for recreational purposes has gone gang busters. A million bicycles were sold each year between 2001 and 2009 in Australia. If mandatory helmets are such a deterrent, how come recreational cycling – which is very much a discretionary activity – has boomed since the 1990s?

I think helmets are more of an issue in relation to the failure of Melbourne Bike Share (although not the primary cause), but it’s important to understand that it’s getting access to a helmet that’s the problem with the Bixis, not the fact of having to wear one. Some perspective is needed here too – there are 600 Bixis in Melbourne, but millions of bicycles in residents’ homes. It’s the latter that matters for Melbourne’s future.

There’s merit in the argument that mandating helmets was probably a mistake, but I very much doubt it’s a significant deterrent to cycling. It’s a second order issue. The big obstacle to more cycling in Australia is road safety, not mandatory helmets. Let’s get our priorities in order and focus on the main game.

Helmet protection confirmed . . . again

25 November 2010. A bike rider who crashes without wearing a helmet is five times more likely to suffer serious head injury than a rider with a helmet, according to an analysis of crash victims by Royal Prince Alfred Hospital (RPAH), Sydney.

The researchers compared the injuries suffered by more than 300 injured riders at the hospital between 2008 to 2010.

“Non-helmet wearers had five times higher odds of intracranial bleeding or skull fracture compared with helmet wearers,” Dr Michael Dinh, the lead researcher, said.

The results are in line with similar international studies into whether helmets reduce head and brain injuries.

The findings are contained in a letter written by Dr Dinh and six colleagues at the RPAH’s emergency and trauma departments, to the Medical Journal of Australia.

“It is the opinion of the trauma service at RPAH, based on these findings, that mandatory bicycle helmet laws be maintained, and enforced as part of overall road safety strategies,” the authors say.

“The benefits of helmet use need to be placed in the context of lifetime costs of severe traumatic brain injury, estimated to be around $4.8 million per incident case.”

The researchers also looked at the cases of almost 1000 riders who were injured in accidents going back to 1991.

During that time the number of riders presenting at RPAH emergency tripled, in line with the rising popularity of bike riding in Sydney.

But as the number of injured rider went up, their rate of serious head injury decreased significantly, from 10.3 per cent in 2005 to 2.5 per cent in 2009.

“The number of cyclists sustaining severe head injuries has remained consistently low over the long-term, with an apparent decline in the rate of severe head injuries in admitted patients since 2005,” said Dr Dinh.


1: you would not expect hospital physicians to say anything else – they only have to deal with what comes through the hospital door

2: no assessment of the discouragement to ride that helmets have and how that affects public health in particular and the environment in general (carbon pollution)

and another two

3: the study is of 300 injured riders at the hospital and therefore may only represent a small fraction of bicycle accidents for which the helmet was totally ineffective

4: quote “But as the number of injured rider went up, their rate of serious head injury decreased significantly, from 10.3 per cent in 2005 to 2.5 per cent in 2009.” – the inference being that bicycle helmets were responsible, but then it also may have something to do with slower riders, and more cyclists, the latter being a known safety factor


5: there are so many well intended people bent on removing any sense of personal responsibility

Argument on the effectiveness of bike helmets continues



Published: February 16, 2010

The British Medical Journal (BMJ) has published an article that gives substance to concerns about cycle helmets.

Australian statistician Dr Dorothy Robinson argues that there is no evidence from countries that have enforced the wearing of cycle helmets that there has been any benefit to public health. Robinson reviewed data before and after helmet legislation in Australia, New Zealand and Canada and believes helmet laws discourage cycling and produce no obvious response in the number of head injuries. She says:
“This contradiction may be due to risk compensation, incorrect helmet wearing, reduced safety in numbers (injury rates per cyclist are lower when more people cycle), or bias in case control studies.” She suggests that helmet laws are counterproductive and that governments should instead focus on measures that lead to clear drops in casualties, such as campaigns to against speeding, drink-driving, and failure to obey road rules. “Helmet laws would be counter productive if they discouraged cycling and increased car use,” says Robinson. “Wearing helmets may also encourage cyclists to take more risks, or motorists to take less care when they encounter cyclists.”
The Journal also published a counter-opinion by four academics who have long pressed for helmet laws. The crux of their argument is that it doesn’t matter if helmet laws discourage cycling (which, for the first time, that admit takes place) because people may take other forms of exercise instead, although they offer no evidence that this occurs.
‘Rapid Responses’ now appearing on the BMJ website suggest that Robinson’s arguments are more convincing and give much other evidence in support.

Another study called The Potential for Cycle Helmets to Prevent Injury – Review . D.Hynd UK 2009 looks at the effectiveness of helmets as such and concludes that helmets protect the head…at a first glance over the 122 pages it does not seem to address the impact of helmets on cycling participation.  I will look at the report in more detail at some later stage.

Brisbane’s cycle hire scheme and bike helmets



Published: April 13, 2010

Brisbane is about to start a bike hire scheme with some 1500 bikes at locations around the city.  The contentious issue of compulsory helmet use, and whether that will affect the success of the scheme is the subject of an ABC news article that can be found here

A brief scan of the comments indicates a large degree of support for compulsory helmet use.

Scrap bike helmet laws



Published: August 16, 2010

Associate Professor Chris Rissel, from the Sydney Universitie’s School of Public Health asserts that helmets put people off cycling and points to the very low risk of head injury to people who ride along quiet streets. He also points out that head injuries in cyclists declined BEFORE the helmet laws were introduced. The story is on the ABC News website.

The research paper of  A.Voukelatos and C.Rissel is called “The effects of bicycle helmet legislation on cycling-related injury: the ratio of head to arm injuries over time”Bicycle helmet legislation – Rissel 2010. The researchers examined over 40’000 cases of cyclist hospitalisation over a 20 year period, looking for a correlation between head and arm injuries. Their paper was based on the assumption that even if the numbers of cyclists has dropped over time, the relative injury rates (head versus arm) should remain unchanged unless some factor is differentially impacting on one type of injury, for example, helmet use reducing head injuries but not affecting arm injuries.

The Interview Record is here

The item attracted dozens of comments.

The “West Australian” also picked up the story West Australian Bicycle Helmet Laws not needed

Earlier related post on our website:




Better-fat-than-dead (deals with the innitial lack of success of the Melbourne bike hire scheme

Safe riding advice, including a comment on helmet use


There is also a paper by Delia Hendrie of the University of Western Australia, who seems to confirm a reduction in head injury for cyclist after the introduction of the helmet laws, but leaves open if that could also be due to the reduction of cycling activities after the helmet laws were introduced.

An earlier presentation made by Bruce Robinson in 1996 questions if the legislation resulted in a decrease in head injuries.

The Cyclist Action Group wrote to Chris Rissel, and we received his paper as a result.

From: Bruce Robinson

Dear Prof Rissel,

I saw your statements in the West Australian and on the ABC News Online. I am not sure if you are aware of the WA data which strongly supports your suggestion that helmet legislation should be revoked.  As I understand it, the WA Hospital Morbidity Database, which goes back to 1971, is of world standard and allows a very detailed assessment of bicycle crash injuries, and also the essential comparison with similar injuries to other road users. Hendrie’s paper is unique in that it compares head-injury rates compared to the rates of other injury types amongst cyclists to similar ratios amongst other road users.  This seems an obvious way to overcome a lot of the biases in the more simplistic approaches to head injury rates. I think there is a very good case that public health levels in WA have been significantly reduced due to the helmet legislation.  (a) the helmet legislation has been very largely ineffective in reducing the risk of head injury (for reasons which escape me) and (b) the public health benefits of physical activity greatly outweigh the marginal risk of not wearing a helmet if one chooses. I am concerned that the “injury prevention industry” seem to over-rule a more general public health perspective in the bicycle helmet legislation debate. I enclose a copy of Delia Hendrie’s helmet evaluation paper (while she was at UWA), and a link to an early amateurish one I presented at a conference in 1996 ( ) (The Hendrie report was published as part of the proceedings of a conference sponsored by the Road Safety Council in 1999.   The paper is available (but not easy to find) on the WA Office of Road Safety website at

Bruce Robinson, President, Cyclists’ Action Group

Now there is yet another source of doubt

Nagging doubts raised over helmet safety

Deborah Gough

April 2, 2011

FRESH doubts have been cast about how useful helmets are in preventing head injuries to cyclists.

An analysis by Norwegian researchers of existing studies has suggested previous scrutiny was biased towards helmets and relied too heavily on research into 1980s ”stack-hat” style hard-shell helmets. They argued that today’s ”soft-shell” helmets were less effective at reducing brain injuries.

The paper, to be published in next month’s edition of the international journal Accident Analysis and Prevention, found helmets reduced head injuries by 55 per cent when statistics included all helmet styles and data from previously omitted studies. Studies with both helmet styles, but without the omitted results, showed they reduced head injuries by 60 to 75 per cent. Hard-shell helmets have been found to reduce head injuries by as much as 88 per cent.

The paper, by Norway’s Institute of Transport Economics, found that hard-shell helmets protected against neck injuries but that the modern soft-shell helmets preferred by most riders today may cause neck injuries.

The findings are certain to fire further debate about Australia’s compulsory helmet laws, which are already being questioned in the cycling and research communities and overseas.

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