2011 April

Are Helmets Dangerous?

The Mayor of DC showing just how serious they are about helmets and safety

We’re pretty sure most people would agree that all things equal, you are better off wearing a helmet than not, if you happen to be in an accident.  Hell, even if tying a rubber chicken to you head increased your survivability by 1%, you’d be crazy not to tie one on if you knew you would be coming off your bike.

Head Protection a la Mr Bean – clearly you’d need to cut holes for vision.

But dangerous? How could that be possible?

Of course there is some evidence that helmets cause some types of neck and brain injuries by increasing the rotational forces on the head & neck; this serious brain injury type is known as diffuse axonal injury (DAI).  Granting that the DAI thesis is true for a moment, the real question is whether the improved protection from linear deceleration outweighs the possibility of a DAI from rotational forces – something we are not sure about (if you have any evidence to the contrary, please enlighten us – we can’t find any).

Helmets can be dangerous however, when one starts to believe the misinformation peddled in many Anglo-American road safety and helmet campaigns.  A “helmet will save your life” and “It’s not safe to ride without a helmet” are dangerous ideas because 1) they aren’t true and 2) they alter cyclist & non-cyclist behaviour in ways that lead to increases in cycling collisions and injuries.

Cyclists who think they are more protected than they really are take more risks.  Motorists who think cyclists are safer than they really are expose them to more risks.  And of course, politicians who promote helmets as a panacea for bike safety, while ignoring the causes of road-related injuries, put cyclists at much greater risk. Not to mention the subconscious effect of portraying cycling as inherently dangerous – ‘dangerising’ it – when it is as safe as walking.

So perhaps it would be more accurate to state that while helmets are not dangerous per se, the over-promotion of their effects and mandating their use most certainly is dangerous.

Hat tip to @vebah for the photo

Update: It seems some helmet makers are now publicising the dangers of DAI.  The European Road Safety study (COST327) into motorbike head injuries found the majority of serious head injuries were caused by rotational forces!

Safety without helmets

How do the Dutch have the worlds best cycling safety record while simultaneously having the lowest helmet usage rates?  This video gives a hint.

Despite the terrible music and pain of watching people riding over black ice, it does shed a light on the real nature of cycling accidents.

Hat tip to @carltonreid & @kim_harding

Publication bias and time-trend bias in meta-analysis of bicycle helmet efficacy

Rune Elvik from the Institue of Transport Economics has recently published an examination of publication bias in helmet research meta-analysis.  From the abstract:

This paper shows that the meta-analysis of bicycle helmet efficacy reported by Attewell, Glase, and McFadden (Accident Analysis and Prevention 2001,  45–352) was influenced by publication bias and time-trend bias that was not controlled for. As a result, the analysis reported inflated estimates  of the effects of bicycle helmets. This paper presents a re-analysis of the study. The re-analysis included: (1) detecting and adjusting for publication bias  by means of the trim-and-fill method; (2) ensuring the inclusion of all published studies by means of continuity corrections of estimates of effect rely on  ero counts; (3) detecting and trying to account for a time-trend bias in estimates of the effects of bicycle helmets; (4) updating the study by  including recently published studies evaluating the effects of bicycle helmets. The re-analysis shows smaller safety benefits associated with the use of bicycle helmets than the original study.

The study is a meta-meta-analysis: it analyses earlier analysis used by others who analysed earlier primary analysis.  As such, it doesn’t offer any new empirical evidence into helmet use, efficacy, risk exposure or the effects of helmet laws.  What it does do however is highlight biases in earlier meta-reviews where a number of primary studies that were not conclusive with their findings were excluded.

After controlling for these biases, Elvik concludes:

  • Bike helmets reduce the risk of head injuries, all other things equal, although not by as much as previously reported.
  • Bike helmets increase the risk of neck and rotational injuries.
  • Older studies show a small postive reduction in injuries when considering head, neck and face as a whole.
  • Newer studies of helmet efficacy “summarised by a random-effects model of analysis, indicate no net protective effect.”
  • The results from studies of the effectiveness of helmet laws are not consistent with the claims of helmet efficacy.  Mandatory helmet legislation doesn’t produce the effects that pro-helmet research predicts it should.

So while no new primary data is presented, this study is still interesting in that it highlights the dilemma for promoters of helmet legislation – not a single study anywhere in the world has shown that helmet laws make cycling safer.  Helmet use may reduce the risk of some injuries in the event of an accident, but helmet laws have other unintented consequences that negate any benefit of helmet use and can actually make cycling more dangerous.

Are helmet laws holding back cycling in Australia? You can do something about it. Write to your State MP and ask them to support helmet freedom.

Helmet Laws Are Unhealthy

A new website has appeared which promises to be a nexus of quality academic journalism in Australia. It is called ‘The Conversation‘ and so far we are impressed with the content.

As Helmet Freedom’s focus is to free us from our draconian all-age mandatory helmet laws, we have picked up on one article in particular, “Ditching Bike Helmet Laws For Better Health“, by Associate Professor Chris Rissel who is the Professor of Public Health at The University of Sydney.

Professor Rissel writes:

“This poses a puzzle – if bicycle helmets protect the head from injury, surely if all cyclists wore one there would be fewer head injuries?”


“Increased physical activity added 3 to 14 months to a person’s life expectancy, while the life expectancy lost from air pollution was 0.8 to 40 days. Increased traffic accidents wiped 5-9 days off the life expectancy.

It is clear that the benefits of cycling outweigh the risks, with helmet legislation actually costing society more from lost health gains than saved from injury prevention.”

Why not add your voice to helmet choice, and write a letter? Society will thank you.

Take action today and start enjoying the ride! Read more