December 13, 2006

Bicycle Helmets: To Wear or not to Wear, That is the Question

You might think that the utility of wearing bicycle helmets has been so well established, that there is no serious questioning of laws requiring their use. Well, as with everything else, there are two sides to the issue. While the Insider always leans toward the disciplined use of personal protective equipment such as helmets, it's important to keep an open mind.

Let's begin with helmet advocacy. I cannot imagine a more challenging environment for cyclists than New York City. One study of the city's fatal bicycle incidents (225 fatalities over a 10 year period) found that helmets probably reduce the risk of death. The data is pretty compelling:
: Almost three-quarters of fatal crashes (74%) involved a head injury.
: Nearly all bicyclists who died (97%) were not wearing a helmet.
: Helmet use among those bicyclists with serious injuries was low (13%), but it was even lower among bicyclists killed (3%).
: Only one fatal crash with a motor vehicle occurred when a bicyclist was in a marked bike lane.
: Nearly all bicyclist deaths (92%) occurred as a result of crashes with motor vehicles.
: Large vehicles (trucks, buses) were involved in almost one-third (32%) of fatal crashes, but they make up approximately 15% of vehicles on NYC roadways.
: Most fatal crashes (89%) occurred at or near intersections.
: Nearly all (94%) fatalities involved human error. The study notes that "all New Yorkers, whether pedestrians, bicyclists or motorists, can help prevent crashes by following traffic signs and signals and respecting other road users." [To which we add, "Yeah, right."]
: Most bicyclists who died were males (91%), and men aged 45–54 had the highest death rate (8.1 per million) of any age group.

So, if you are a 45 year old male cyclist riding in Manhattan without a helmut, be extra careful when approaching an intersection. To which the cyclists respond, "Yeah, right!"

The Contrary View
Two contrarian views have popped up in the news. In the first, a New Zealand advocacy group rails against the mandatory use of helmets. Cycling Health Inc spokesperson Graeme Trass says, "Well-meaning people believe the helmet law keeps cyclists safe. However, the evidence in New Zealand and overseas shows it discourages cycling and harms the overall health of the population." In other words, some people who might normally ride a bike avoid doing so because they dislike the helmets. Why? According to a study by Massey University researcher Kane Hopkins, women and young people in particular said they avoided cycling because of the effect on their hair-styles. (Not an issue for men, apparently, even though the New York study indicates that men might be less likely to wear a helmet - and more likely to die in an accident. Hmm.)

The New York Times Sunday Magazine (registration required) ends the year with a number of brief profiles of provocative and cutting edge issues. The recent issue included another possible argument against bicycle helmets. Ian Walker, a psychologist at the University of Bath, was intrigued by an urban myth involving cyclists: For years, cyclists who ride on city streets have sensed that if they wear helmets, they are more likely to get hit by a car.

Walker decided to put the myth to a scientific test. He rigged his bicycle with an ultasonic sensor that could detect how close cars came to him when they passed. He spent a couple of months on the road, with and without a helmet, until 2,500 cars had passed him. (Let's hear it for the scientific method!) Examining the data, he found that when he wore a helmet, motorists passed by 3.35 inches closer than when his head was bare. So riding with a helmet appears to be a little more dangerous than riding without.

Walker theorizes that helmets change the behavior of drivers. Motorists regard a helmet as a signal that the cyclist is prudent and experienced and thus can be approached with less caution. "They see a helmet and think, Oh, there's a serious rider," Walker says. "And you get hit." By contrast, drivers apparently view helmetless riders as less reliable and more at risk, so drivers are more cautious when passing them.

Walker's study will be published next year in the journal Accident Analysis and Prevention. When Walker circulated his preliminary findings, he got a lot of angry emails. Helmet advocates accused him of opening the door to mayhem and carnage on the roads. Walker takes a different view. He thinks that by responding to a helmet, drivers are making unconscious judgments about cyclists. He thinks the answer is not necessarily in foregoing the use of helmets, but in educating drivers that passing helmeted cyclists is no different from passing those without helmets.

Walker personally has little use for helmet laws or, for that matter, helmets. He rarely wears one. During his study, he was struck twice, once by a bus and once by a truck (larger vehicles, it's worth noting, just as was found in the New York study). Both times he was hit, he was wearing a helmet. So Walker seems to believe he's safer without the helmet. It would be interesting for him to present his findings to an audience of the families and friends of the 225 deceased riders in New York City. That would be one scientific symposium worth the price of admission.



I wonder if he had been hit twice without a helmet if he would have survived to write his results?

For many years, I've been deeply involved in seat belt legislation, especially that which targets children. When I used to give speehes about it I would invariably get a dissenting view from some audience member who would report that his " life had been saved" because he had been "thrown from a car during a crash." And if he'd been restrained by a seat belt he would have died in the crash because the car burst into flames after impact.

The audience would nod its collective head at the power of this argument.

I have to admit that I relished the silence that followed when I then asked for similar testimony from the other 98% of the people thrown from cars during crashes who had not survived to tell the story.

Mr. Walker's experiment is flawed by the fact that he can't control for his own behavior--he treats his bicycle as a fixed point against which he measures drivers, but he may actually be riding an average of 3.5 inches farther into the street when he wears a helmit (especially if he has a bias towards riding bare-headed). There are also questions of sight lines and such that aren't answered by the experiment.
I'm a 59 year-old Clevelander who has broken through two helmits by falling off the bike, through dumb moves of my own, with nary a car in sight--so I will continue protecting my poor stupid head with the helmit, no matter what the conditions in Manhattan!

Because bicycle helmets were believed to be beneficial, some countries passed helmet laws. Even when helmet wearing increased from 20-30% of all cyclists to 70-80%, expected reductions in head injuries did not materialise. A summary of the evidence was published in the BMJ in 2006 – see

Investigations revealed that much of the evidence used to promote helmet laws was flawed. For example, there is no check box for helmet use on many US State agency forms. Instead of being coded as unknowns, cases were often incorrectly recorded as non-wearers in the FARS database, grossly underestimating helmet wearing rates of fatally injured cyclists.

Coronal or crash-scene investigations into the cause of cyclist fatalities provide more reliable information. The vast majority find no evidence that a bicycle helmet would have helped. Most bicycle fatalities result from for high impact collisions with motor vehicles. Realistically, how could a flimsy bicycle helmet (tested by measuring forces when a headform is simply dropped, not smashed into a car) possibly help?

Evidence that helmets prevent serious head injury is also flawed. It was based on similar statistical techniques to those that found hormone replacement theory (HRT) reduces heart disease by 50%. Some years later, randomised trials were conducted showing that HRT actually increases the risk of heart disease!

Although helmet voluntary wearing may be beneficial, especially to prevent minor wounds, helmet laws have other consequences, such as reduced cycling. A Danish study found that people who cycled to work had 40% lower mortality than their counterparts. Reduced cycling because of helmet laws not only means less exercise (and perhaps increased risk of brain damage from strokes or heart disease), people drive instead of cycle (increasing pollution and greenhouse gas emissions) and those who continue to cycle are deprived of Safety in Numbers.

Perhaps the best way of seeing the overall picture, is to examine ‘Safety in Numbers’ comparisons for different countries - see Would you prefer to be a non-helmeted cyclist in Holland or Denmark, with a fatality rate of less than 2 per hundred million km, or a helmeted US cyclist with a risk of more than 10 fatalities per 100 million km?


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This page contains a single entry by Jon Coppelman published on December 13, 2006 10:43 AM.

News Roundup: trucks, trains, TRIA, and more was the previous entry in this blog.

Health Wonk Review - Issue Number 22 is the next entry in this blog.

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