Do Bicycle Helmet Laws Do More Harm Than Good?

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Whenever I write about bicycle helmets, (which I always wear) we get comments that invariably say:

Studies have determined that the helmet is even counter-productive, where it became mandatory, the use of bicycles decreased dramatically, and the less there are bikes in the streets, the less drivers get accustomed to their presence. Dutch do not wear helmets, and they know about bicycles.

So which studies? What do they really say? It is a good time to ask, because a new one just came out that claims that "bicycle helmet laws could do more harm than good." But one has to separate the issue of wearing helmets from the issue of helmet laws.

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1. Do helmets actually work?

The facts are there and are pretty obvious: If you are going to bang your head onto concrete or metal, you are going to be better off with a helmet than without. A "case-control study of the effectiveness of bicycle safety helmets" published in the New England Journal of Medicine found that:

Riders with helmets had an 85 percent reduction in their risk of head injury and an 88 percent reduction in their risk of brain injury . We conclude that bicycle safety helmets are highly effective in preventing head injury. Helmets are particularly important for children, since they suffer the majority of serious head injuries from bicycling accidents.

OK, that seems pretty obvious and a pretty big number. But why do people bang their heads? Usually because of interactions with cars. (image from Cyclist's Head Run Over By Truck, Saved by Helmet)

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2. Dutch do not wear helmets, and they know about bicycles

Absolutely true. But the circumstances and infrastructure are completely different. They have established separation of cars and bikes, a network of bike lanes unmatched in the world going back almost a hundred years. They have presence and numbers that do not exist in North America. Even the author of the report on the effectiveness of helmet laws is quoted in the New Scientist:

de Jong, a native of bike-loving Holland, makes clear that he would not discourage people from wearing helmets. "I go to Holland and places like that, and I don't wear a helmet," he says. "I used to live in London, and I wore a helmet all the time."

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3. Does wearing a helmet encourage more dangerous riding practices?

In her study, "Do enforced bicycle helmet laws improve public health?"
which will be discussed later, Dorothy Robinson finds the opposite:

Cyclists who chose to wear helmets commit fewer traffic violations, have higher socioeconomic status, are more likely to wear high visibility clothing and use lights at night.

So clearly putting on a helmet does not turn you into a crazed cyclist.


4. Is there "safety in numbers"?

Absolutely. Peter Jacobson's 2003 study concluded:

-Where, or when, more people walk or bicycle, the less likely any of them are to be injured by motorists. There is safety in numbers.

-Motorist behavior evidently largely controls the likelihood of collisions with people walking and bicycling.

-Comparison of pedestrian and cyclist collision frequencies between communities and over time periods need to reflect the amount of walking and bicycling.

-Efforts to enhance pedestrian and cyclist safety, including traffic engineering and legal policies, need to be examined for their ability to modify motorist behavior.

- Policies that increase walking and bicycling appear to be an effective route to improving the safety of people walking and bicycling.

5. Are Helmeted Cyclists "car magnets?"

Our commenter suggested that drivers are less careful around helmeted cyclists. ("this cyclist jerk seems well enough protected to me, no need to be too careful around him").

There appears to be some truth to this. A study published Accident Analysis and Prevention was summarized in

test cyclists were given 8.5cm (3.3 inches) more clearance by cars if they were not wearing helmets. When the researchers donned female wigs they got more clearance, 14cm (5.5 inches) more than apparent males in helmets. They did not report on what a skirt and helmet combination would do. The author was hit by a bus and a truck during the experiment, and was wearing a helmet both times.

TreeHugger Warren was not so sure about this and wrote about it here in TreeHugger.

So looking at the evidence so far, we need a lot more good bike infrastructure and separated bike lanes, a lot more cyclists to get that safety in numbers effect, and if you are going to wear a helmet, put a wig over it. But now we get to the crux of the issue. Back to the comment:

Studies have determined that the helmet is even counter-productive, where it became mandatory, the use of bicycles decreased dramatically...

No. Had our commenter said "studies have shown that helmet laws are counterproductive" he would have a case. Because there is some evidence that "where it became mandatory, the use of bicycles decreased dramatically". But don't mix the benefit of wearing a helmet with the benefit of helmet laws.


6. Do Helmet Laws reduce the use of bicycles dramatically?

Perhaps. In Australia. For a while. All claims that helmet laws reduced the use of bicycles go back to a study by Dorothy Robinson of the University of New England in Australia, summarized in Injury Prevention.


Robinson writes in the summary:

the effect of unpopular helmet laws on cycling activity is readily seen. In Melbourne, surveys were conducted pre-law in May 1990 and post-law in May 1991, at the same 64 sites and same observation times. Counts of child and adult cyclists declined by 42% and 29% respectively. In total, 297 more helmeted cyclists were counted than pre-law, compared with 1100 fewer cyclists. It's as if the law didn't so much encourage helmet wearing as discourage cycling!

In her original study (PDF download here) she says "Cyclists often consider helmets hot, uncomfortable and inconvenient." She also claims that "the frequently cited example of legislation in Ontario not discouraging cycling is misleading."- can it be that Australian results are biased because it is hotter there, and in more temperate Ontario helmets are not so hot and uncomfortable?

Finally, we come to the latest study by Piet de Jong, which concludes that helmet laws are actually bad for public health. He looks at the cardiovascular and fitness benefits of cycling and the drop in the number of cyclists projected by Dorothy Robinson and concludes that:

Helmet laws like those in effect in Australia levy a substantial cost on healthcare systems because savings from fewer head injuries pale in comparison to the costs incurred by decreases in cycling.

But the entire premise of the study is based on the decrease in cycling as projected by Robinson, and as one critic noted:

"What she has never shown to my satisfaction, or that of other critics of her work, is how long the decline persisted," says Barry Pless, an epidemiologist at Montreal Children's Hospital in Canada.

More in the New Scientist and de Jong's original study in PDF here.
1. We need better biking infrastructure to separate us from stupid drivers. That is the lesson from the Netherlands, that we need more cyclists and better bike paths more than we need helmets.

2. Don't confuse helmets with helmet legislation.
I will concede the point that helmet legislation may cause a reduction in the number of cyclists, which can be counterproductive if we are trying to promote cycling. I might even go so far as to accuse governments of shifting responsibility to the heads of cyclists and away from the drivers of cars by putting cyclists in such lousy infrastructure with lousy drivers.

3. Helmets work. it is silly to say that they don't; if you are going to crack your head into something they will protect it. If you don't live in the Netherlands or Copenhagen or somewhere with lots of cyclists and a decent infrastructure, you should wear one.

4. Compromise?
In Ontario, kids have to wear helmets, adults don't. If you grow up with a helmet on your head or a seatbelt on your lap, you feel naked without it. Eventually, almost everyone will.

More on Bike Helmets
To Helmet or Not To Helmet; This is the Question
In Denmark, the Police Give out Bike Helmets and Hugs
A Brain Surgeon on Bicycle Helmets
Cyclist's Head Run Over By Truck, Saved by Helmet
Dutch Cycling: Remember the Phone, Forget the Helmet

Do Bicycle Helmet Laws Do More Harm Than Good?
Whenever I write about bicycle helmets, (which I always wear) we get comments that invariably say:

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