Weird Science: Do Helmets Attract Cars to Cyclists?


Following Alex Marshall’s essay on bicycle helmets this morning, Scientific American recently reported on a paradox emerging in relation to helmets and traffic accidents. It seems that drivers are a lot more scared of hitting you if you leave your protective gear at home:

Spring is in full swing now, and a number of the straphangers in New York City are getting new tubes and tires and dragging their bikes out of storage. Bicycle riding is the skill you reportedly never forget, but there’s a raging debate about whether or not you should forget your helmet when you hop on your two-wheeler.

Last September a plucky psychologist at the University of Bath in England announced the results of a study in which he played both researcher and guinea pig. An avid cyclist, Ian Walker had heard several complaints from fellow riders that wearing a helmet seemed to result in bike riders receiving far less room to maneuver-effectively increasing the chances of an accident. So, Walker attached ultrasonic sensors to his bike and rode around Bath, allowing 2,300 vehicles to overtake him while he was either helmeted or naked-headed. In the process, he was actually contacted by a truck and a bus, both while helmeted-though, miraculously, he did not fall off his bike either time.

His findings, published in the March 2007 issue of Accident Analysis & Prevention, state that when Walker wore a helmet drivers typically drove an average of 3.35 inches closer to his bike than when his noggin wasn’t covered. But, if he wore a wig of long, brown locks-appearing to be a woman from behind-he was granted 2.2 inches more room to ride.

Walker, whose much-publicized report may inspire a new generation of bareheaded riders, won’t make any specific recommendations to other cyclists, though he notes that when it comes to riding in traffic, motorists are the real problem.

Photo: Sheila Steele/Flickr

  • So, I haven’t actually read Ian Walker’s study but couldn’t it just be that HE tended to ride closer to cars when he was wearing a helmet? How did he control for that?

    If anyone actually reads through the whole study, let us know.

  • Greg Raisman

    Bicyclist deaths by helmet use in US, 1994-2005

          No helmet use  Helmet use        Total*
    Year    Num      %      Num     %       Num
    1994 	776 	97 	19 	2 	796
    1995 	783 	95 	34 	4 	828
    1996 	731 	96 	27 	4 	761
    1997 	785 	97 	23 	3 	811
    1998 	741 	98 	16 	2 	757
    1999 	698 	93 	42 	6 	750
    2000 	622 	90 	50 	7 	689
    2001 	616 	84 	60 	8 	729
    2002 	589 	89 	54 	8 	663
    2003 	535 	85 	58 	9 	626
    2004 	602 	83 	87 	12 	722
    2005 	673 	86 	76 	10 	782

    *Total includes other and/or unknowns


  • Greg (or anyone),
    Can you explain why in 1994, 97% of cyclists killed were not wearing helmets, and why in 2005, only 86% of cyclists killed were not wearing helmets.

    That doesn’t make sense to me, and I’m wondering what other factors contribute to that. The total fatal numbers from the first and last years are almost identical, just the ratio has changed.

  • The answer is pretty obvious, isn’t it?

    A helmet camouflaged under a wig of blond tresses.

  • e.p.c.

    Would help to know the number of cyclists per year or even the number of injuries sustained by cyclists in order to interpret the fatality statistics. If the number of cyclists wearing helmets increased substantially between 1994 and 2005, it would not be unreasonable for the number of fatalities for helmet wearers to increase.

    For example, the 2005 report says that 784 pedacyclists were killed but 45000 were injured. Unfortunately the FARS website is so painfully slow I can’t pull up the 1994/1995 data (

    There’s a summary report here:

  • e.p.c. beat me to the punch.

    Put another way, helmets don’t prevent all fatalities. The more people wear helmets, the more likely helmet-wearers will be among those fatalities for which a helmet is not protection.

  • e.p.c.

    Didn’t realize the URL I posted was the same as in the second comment.

    The FARS system is painful to use but does seem to have a lot of data on cyclist and pedestrian injuries and fatalities, one just has to be very patient to use it.

  • anonymous

    How about the total percentage of bicycle miles traveled with or without a helmet? Maybe more people are wearing helmets? Maybe more people are riding bikes too, and because more people are wearing helmets, there are fewer accidents. Or maybe the number of accidents stays the same because there’s more awareness of bikes with more bikes on the road. These statistics say nothing at all beyond how many cyclists died while wearing or not wearing helmets.

  • Thanks EPC and Sean. Clear.

  • a few years ago i read an article in the ny times magazine about a brain surgeon who was undergoing extreme physical and mental rehabilitation after being thrown from his bicycle by a bump in a country road and incurring a massive brain injury. ironically, he was now a patient of the regimen he himself had developed as a surgeon. there were no cars involved in his accident, and he was not wearing a helmet, which would have prevented the injury.

    i’ll take the helmet.

  • As a dedicated non-helmet user myself, I take comfort in the fact that pratically everywhere else in the world few wear helmets (well, not Australia, it’s mandated.) And that I grew up in a country where there were thousands of non-helmeted cyclists and I rarely heard of an accident.

    So I wonder: are we just more risk-averse? Are more vehicles out to get us here? Are we worse bicyclists?

    I think also I can point out that in most other countries, cycling is more common, and is used for transportation, so you don’t have messengers and spandex tornoadoes whizzing around too fast for their own good (flame suit on.)

  • Aaron, from what I remember (sorry I can’t pull it up immediately), he placed a device on his bicycle that measured the distance between himself and every car that passed him. According to the device, the average distance between himself and the passing motorists was much smaller when he rode without his helmet.

    He must have ridden an awful lot — and maybe on really skinny streets, too — but he said he was brushed several times by cars. Most of those times was when he was wearing his helmet.

    If you think about it, this study probably also supports the idea that removing all signs and markings from the road leads motorists to drive slower and be more careful.

  • Aaron W

    I can’t believe people are still referencing this junk science “study.”

  • @Aaron (both Aarons!): Yes, the science of this study is positively retarded. I mean, come on, the “researcher” was also the test subject. That’s pretty much the first sign that any given “scientific” study is a steaming pile of bullshit.

    There are seven ways to detect bad science by just the smell of it. This study violates four of them.

    Use your common sense and just imagine how many ways this study could be faulty. In addition to the previously-mentioned ways in which the tester himself could have deliberately or accidently affected the measurements, there are many common-sense holes and flaws. Drivers don’t give a damn about cyclists, helmets or not — are we supposed to beleive that drivers have enough time to make this call. Drivers who might normally harass a male cyclist might be a little more gentlemanly to a female cyclist (as the guy was pretending to be). One or two cars in a single test session driving five feet away from the cyclist could easily skew the average distances (note he uses average and not mean distance, another sign of crap science).

    Wear your damn helmets, kids.

  • Sproule Love

    Hear, hear. This study is total hooey.

    To the “dedicated non-helmet user” in post no. 11: if you’re going to make such preposterous claims, particularly here on SBlog, you might want to produce some data to back them up. Just because you “grew up in a country where there were thousands of non-helmeted cyclists and (you) rarely heard of an accident” doesn’t mean there weren’t any. What an odd object of dedication.

  • To #15: It wasn’t a claim, it was a valid observation. You weren’t there, I was. And obviously I don’t imply there were no accidents, it’s that people were not dying like flies sans helmets.

    It’s tiring to hear people deny reality, which in this case is that the % of helmet users in countries not mandating them is extremely low (France and Netherlands

  • Old thread though this may be the subject of helmet use in the cycling world is always a hot topic for discussion.

    As a lawyer in the UK working with injured cyclists daily – there is no question that wearing a helmet is the only choice one can make. As your head hits the tarmac and you have less than half a cm of skull to protect you from serious harm, ask yourself the question…”do you feel lucky?”

    Wear a helmet – take no chances – stay safe


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