Study: Commuter Cycling "Less Safe" with Bike Helmets

By Ryan McGreal
Published September 12, 2006

I'lve always assumed that while bicycle helmets don'lt provide an actual cone of invincibility, they at the very least do more good than harm.

Now a study from the UK has thrown that assumption into question:

Cyclists who wear protective helmets are more likely to be knocked down by passing vehicles, new research from Bath University suggests.

The study found drivers tend to pass closer when overtaking cyclists wearing helmets than those who are bare-headed.

The researcher, Psychologist Dr. Ian Walker, "used a bike fitted with a computer and an ultrasonic distance sensor to find drivers were twice as likely to get close to the bicycle, at an average of 8.5cm, when he wore a helmet."

Dr. Walker explained:

This study shows that when drivers overtake a cyclist, the margin for error they leave is affected by the cyclist'ls appearance.

By leaving the cyclist less room, drivers reduce the safety margin that cyclists need to deal with obstacles in the road, such as drain covers and potholes, as well as the margin for error in their own judgements.

He is careful to note that the study applies mainly to cyclists who use their bikes for commuting. For recreational cyclists and especially for children, wearing a helmet is unquestionably safer than not wearing one.

With children, especially, helmets offer the best protection against low speed falls and should always be worn. Ontario provincial law requires children under 18 to wear a helmet when cycling.

For bicycle commuters, however, Dr. Walker said, "whether [helmets] offer any real protection to somebody struck by a car is very controversial."

Even if helmets do offer protection, the simple act of wearing a helmet increases the likelihood of being hit by a car. It remains to be seen whether the increased risk of being hit is enough to offset the increased protection from head injury if a cyclist is hit.

Ryan McGreal, the editor of Raise the Hammer, lives in Hamilton with his family and works as a programmer, writer and consultant. Ryan volunteers with Hamilton Light Rail, a citizen group dedicated to bringing light rail transit to Hamilton. Ryan writes a city affairs column in Hamilton Magazine, and several of his articles have been published in the Hamilton Spectator. He also maintains a personal website, has been known to share passing thoughts on Twitter and Facebook, and posts the occasional cat photo on Instagram.


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By asfried1 (anonymous) | Posted September 12, 2006 at 08:57:33

Maybe. However, the scientific method requires that the results be reproduced. Moreover, there are issues of UK drivers vs drivers from other countries. Lots of other issues about this particular methodology.

Lastly, I have commuted 25 miles/day several times a week for years and have only been in one accident with a car. In that accident, my head came down HARD onto the car that hit me - hard to imagine that I would have walked away from that one like I did if I had not been wearing a helmet.

Bottom line - I'm not yet convinced.

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By Ryan (registered) - website | Posted September 12, 2006 at 11:43:39


I'm not convinced either, which is why I wrote, "It remains to be seen whether the increased risk of being hit is enough to offset the increased protection from head injury if a cyclist is hit."

This definitely warrants more research.

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By adrian (registered) | Posted September 13, 2006 at 09:23:10

I think the research might be valid in the UK, but in this case, I think the differences between that country and Canada are significant.

I haven't been to the UK, but if it is anything like the other countries I have been to in Europe, then I bet that the roads are much narrower than they are here, and that many more people use bicycles as a form of transportation, rather than for recreation, and so challenging, off-road riding (mountain biking) is less common.

This matters because on narrow roads, drivers are more likely to get close to you because they have fewer options of space. He says that when wearing a helmet, drivers were twice as likely to get close to him, on average within 8.5cm. Cars never get that close to me when riding. Most cars give me a half-metre at least.

As well, bicycles used for transportation are commonly found on roadways. Bicycles used for recreation are commonly found on trails where no cars are present. In Canada, I'm guessing that not wearing your helmet while riding frequently means riding on challenging off-road trails without a helmet, and that means increased risk. Surely riding headlong into a tree is more dangerous without a helmet.

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By Ryan (registered) - website | Posted September 13, 2006 at 11:30:34

Years ago, my neighbour was a mathematician and worked as a postdoc at Mac. She used to take the Waterfront trail to work, and she never wore a helmet.

I gave her the same lecture that a doctor friend had given me about eating the rest of her meals through a straw, and she reluctantly went out and bought a helmet.

She actually didn't start wearing it until a week later. That day, she was crossing the bridge under the 403, and her tire slid out from under her. She went down like a rock and smacked headfirst onto the surface.

She greyed out and awoke a few minutes later to a small ring of concerned passersby. She had a concussion, but her helmet was destroyed.

That night, she came home and thanked us for saving her from probable brain damage.

I share this long-winded account by way of arguing that the study cited above should be taken as a starting point for similar research here. It applies to British drivers, as adrian points out, and it applies specifically to commuting cyclists - adults who ride on the street to and from jobs and errands.

I think it's important to conduct similar research here and see if the phenomenon is the same. It would also be a good opportunity to see if other variables also affect driver behaviour.

My personal experience, for example, is that drivers tend to give me more clearance when I'm wearing a fluorescent vest. This is purely anecdotal, as I'm only one person and haven't studied the phenomenon systematically, but I think it's a productive avenue of research.

Ultimately, safety measures come down to statistics. The more detailed a picture we have of how the various risk factors interrelate, the better our ability to make sound decisions on improving our safety odds.

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By shaun (anonymous) | Posted September 27, 2006 at 15:29:53

Ryan, whilst i'm glad to hear that your neighbour was not seriously injured, her example is as much evidence for one side of the debate as it is the other:
She presumably rode for years without a significant accident , and the first time she wore a helmet she crashed badly.
No one admits, or possibly is even aware that they make different choises when wearing a helment, but it's all subtle responses that happen due to subconsious risk-perception.

A similar "helmet saved his life the first time he wore it" story was in the local papers here a couple of years ago. It turned out the rider was taking the same route home from school he always has (without incident), but on this occasion he sped right through a stop sign thinking he could get through before a truck.
The author of that article jumped to the same conclusion you did, aparently not even considering what was different on that day that may have caused him to run the stop sign.

Certainly these could just be coincidences, but OTOH they could well explain why injury rates to cyclists are higher in countries where there is greater helmet use. Individual cases can't be used as an indication, only when larger numbers are looked at does the overall picture become more clear.
It seems that most riders have a "helment saved my/friends life story", yet the statistics clearly show there were never that many serious crashes before helmets were popular. Either the crashes would not have caused injury anyhow, or the crashes would not have happened in the first place.

here's a great site about bicycle safety
and another one with facts and figures on the subject of helmet safety:

So spread the word about cycling as the great safe and heathy sport it really is !

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By steven haanah lewm few (anonymous) | Posted June 19, 2009 at 16:22:58

well helmets this size do not seem to protect you

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By Waldofo (anonymous) | Posted September 11, 2009 at 08:42:32

Why do people think a helmet is going to protect the brain - while under a wheel connected to a 10 ton dump truck? The answer is safe bike lanes! What's a safe bike lane? A safe bike lane has a wide physical barrier between automobiles and cyclists. A six inch wide painted stripe just designates a suicide lane NOT a bike lane:

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