Bike Helmet Doubts

By Robin Hanson · September 13, 2010 8:00 am · Comments (51) · ·

As a regular bike rider and helmet-wearer, I was surprised to hear serious substantial doubts about their usefulness (hat tip Brandon Reinhart). I’m pretty sure I’d want a helmet as a soldier or motorcylclist, but that doesn’t mean any helmet helps against any injury. The bike helmet wikipedia page is dominated by helmet skeptics, and there are several well-argued skeptic pages out there, such as this page full of studies.  Consider, for example, the effects of a 1992 helmet law in Western Australia:

WAbikediebikegraphCyclist head injuries didn’t obviously fall a lot, and non-head injuries rose a lot.  There are lots of conflicting studies (e.g,. pro and con), but the best skeptics seem at least as competent as the best pro-helmet researchers.  Selected quotes from wikipedia:

Ordinary cycling is not demonstrably more dangerous than walking or driving, yet no country promotes helmets for either of these modes. … Six times as many pedestrians as cyclists are killed by motor traffic, yet travel surveys show annual mileage walked is only five times that cycled; a mile of walking must be more “dangerous” than a mile of cycling…” The proportion of cyclist injuries which are head injuries is essentially the same as the proportion for pedestrians at 30.0 % vs. 30.1 %. …

Robinson’s review of cyclists and control groups in jurisdictions where helmet use increased by 40% or more following compulsion concluded that “enforced helmet laws discourage cycling but produce no obvious response in percentage of head injuries”. This study has been the subject of vigorous debate. …  The largest [study], covering eight million cyclist injuries over 15 years, showed no effect on serious injuries and a small but significant increase in risk of fatality. … The head injury rate in the US rose in this study by 40 % as helmet use rose from 18% to 50%. …

When mandatory bicycle helmet laws were enacted in Australia, slightly more than one third of bare-headed cyclists ceased to ride their bicycles frequently.[58] In the UK between 1994 and 1996, in areas where cyclist counts dropped, wearing rates increased and where the number of cyclists increased, helmet wearing rates fell. …

A reduction in cycling may lead to an increased risk for the cyclists remaining on the road. … According to one source, the probability of an individual cyclist being struck by a motorist declines with the 0.6 power of the number of cyclists on the road. …  One researcher randomized his helmet use over a year of commuting to work and found that he rode slightly faster with a helmet. …  One small study from England found that vehicles passed a helmeted cyclist with measurably less clearance (8.5 cm [out of] … 1.3 metres) …

Cyclists’ representative groups complain that focus on helmets diverts attention from other issues which are much more important for improving bicycle safety, such as road danger reduction, training, roadcraft, and bicycle maintenance. Of 28 publicly funded cycle safety interventions listed in a report in 2002, 24 were helmet promotions. For context, one evaluation of the relative merits of different cycle safety interventions estimated that 27% of cyclist casualties could be prevented by various measures, of which just 1% could be achieved through a combination of bicycle engineering and helmet use. …

The following countries have mandatory helmet laws, … Australia, Canada, Czech Republic, Finland, Iceland, Israel, Slovakia, Sweden, USA, and New Zealand. … In the U.S. 37 states have mandatory helmet laws, and nearly 9 in 10 adults support helmet laws for children. Israel’s helmet law was never enforced or obeyed, and the adult element has been revoked; Mexico City has repealed its helmet law. … The countries with the best cycle safety records (Denmark and the Netherlands) have among the lowest levels of helmet use. …

Boston had far higher rates of helmet-wearing (32% of cyclists, versus 2.4% in Paris and 0.1% in Amsterdam), Amsterdam had far more cyclists (242 passing bicycles per hour, versus 74 in Paris and 55 in Boston). Cycle helmet wearing rates in the Netherlands and Denmark are very low. … Despite the lack of helmets, cycling in the Netherlands is safer than in any other country.

I plan to be much more casual now about whether I wear a helmet, especially since most of my biking is on mild trails away from cars.

Added 1p: Tim Harford considered such doubts and concluded bike helmets aren’t about safety.

I’ll keep wearing a helmet. I am a) Risk averse and more importantly b) Signalling to my wife that I pay attention to her opinion.

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  1. [...] Another interesting article that lays out several studies and findings about the safety and efficacy of bike helmet use and laws. This article is definitely an interesting read, with LOTS of worthwhile statistics on using bike helmets. What I do find interesting are the these alternative statements that say you motorists may avoid you more (give you a wider berth) if you’re not wearing a helmet, and that riders may actually ride more safely when they don’t wear a helmet. Those things seem counter-intuitive, but I have to wonder if they are true? In studying for our upcoming bike tour, a theme that came up repeatedly is that cars do go around you by a much wider margin if you are pulling a bike trailer. What do you think? Al from Bike 4 Bangers Amplify’d from http://www.overcomingbias.com [...]

    By Statistics on Bike Helmets « Bike 4 Bangers Blog September 13, 2010 at 12:38 pm

  2. [...] recent post on Overcoming Bias includes a number of other arguments for not forcing people to wear bike helmets including this [...]

    By RadarLake » Can bike helmets be bad? September 16, 2010 at 9:25 am

  3. [...] bicycle helmets, do they actually save lives? No, according to many studies. Check out some of them here. One theory is that once a helmet is donned many bicyclists feel much safer, almost invincible, [...]

    By Do bicycle helmets save lives… or make people idiots? « Russmo Rants September 18, 2010 at 12:06 am

  4. [...] even though cyclists suffer only about 7 injuries per million miles of biking, and despite serious doubts if helmets help. Even the proverbial banned lawn darts caused ~30 deaths a year with 10-15 million [...]

    By Overcoming Bias : Status And Glory May 28, 2011 at 12:11 pm

  5. [...] even though cyclists suffer only about 7 injuries per million miles of biking, and despite serious doubts if helmets help. Even the proverbial banned lawn darts caused ~30 deaths a year with 10-15 million [...]

    By Irrational Attitudes Toward Risk | John Goodman's Health Policy Blog | NCPA.org June 3, 2011 at 8:51 am

  6. [...] excellent article sur le pour et le contre de légiférer dans le dossier du port du casque : Overcoming Bias : Bike Helmet Doubts Ce contenu a été publié le roule-roule, et marqué avec casque, contreverse, loi, sécurité. [...]

    By À propos du casque | Roule-roule August 5, 2011 at 8:30 am

  7. [...] People that can write well on behavioural economics are impressive – and I think this article on the effect of legislating bike helmet use on head injuries is just plain fascinating – Overcoming Bias – Bike Helmet Doubts  [...]

    By Digest – 7 August | in great company August 7, 2011 at 12:42 am

  8. [...] excellent article sur le pour et le contre de légiférer dans le dossier du port du casque : Overcoming Bias : Bike Helmet Doubts This entry was posted in roule-roule and tagged casque, contreverse, loi, sécurité. Bookmark [...]

    By À propos du casque | Roule-roule September 8, 2011 at 8:32 am

43 Comments

  1. Aa
    September 13, 2010 at 8:38 am | Reply

    A lot of that doesn’t really seem to support the idea that you personally should wear a helmet less:

    1.) Walking is as dangerous as cycling – I’m curious as to why you would chose to cycle without a helmet rather than walk with a helmet (or at least, you could continue cycling with a helmet as this is socially acceptable). Do you feel that you’re sense that a helmet is not necessary for walking is better supported than your sense that a helmet is needed for cycling?

    2.) Helmet wearing causes you to ignore other dangers – The solution seems to be to focus on the other dangers as well, not stop wearing a helmet.

    3.) Less cyclists on road – this may change your view of the best law but I don’t see why it should change whether you wear a helmet – at least in terms of your own safety.

    The general studies are hard to interpret because the causality could be due to the factors above rather than anything else.

    What were the reasons for your comment that you’d be more causal regarding wearing a helmet? The two main reasons that jump out are:

    1.) You may subconsciously ride safer without a helmet.
    2.) The “small study” that related to the amount of clearance.

    Though once again I’m not convinced wearing a helmet less is necessarily the best response to these (esp if you’re not near cars as then only point 1 applies and you could attempt to compensate for this).

  2. Derek
    September 13, 2010 at 8:39 am | Reply

    Interesting post. I wonder whether wearing helmets causes riders to take more risks on a bike that would result in non-head injuries. For example, it could make them more likely to ride in busy traffic or more likely to treat stop signs and red lights as yields (even if their town doesn’t have such laws).

  3. Khoth
    September 13, 2010 at 8:50 am | Reply

    I think your “especially since most of my biking is on mild trails away from cars” is wrong – the reasons presented for helmet use not being safer don’t apply away from traffic:

    Helmet laws reducing cyclists and denying them safety in numbers doesn’t mean that you personally aren’t safer with a helmet.

    Cars giving you less clearance when you’re wearing a helmet is irrelevant when you’re not in traffic.

    So maybe you should wear a helmet for your cycle trails and take if off when you join the road.

  4. Jim Babcock
    September 13, 2010 at 8:52 am | Reply

    These statistics talk about the number of head injuries, but say nothing about their severity. It seems likely to me that whether there is an injury at all depends only on whether the head was struck, and the effect of a helmet is not to prevent that, but to mitigate the damage.

    • donK
      September 13, 2010 at 11:26 am | Reply

      Of the three major bicycle accidents I have had in my life only one was mitigated by a helmet. I don’t remember the ride to the hospital but I was released within a few hours and of course needed a new helmet.

  5. Khoth
    September 13, 2010 at 9:31 am | Reply

    I’m surprised by the massive increase in the “bruise/abrasion” category on that graph. For a general increase in accidents, I’d expect a similarly sized increase in fractures. Is there something else going on?

    Possibilities that come to mind:
    1. People wearing helmets are more likely to cycle carelessly and fall off in a way that only causes minor injury.
    2. It’s the category that’s most likely to go unreported. Something changed in the collection of the statistics that increased the accident reporting rate (which would throw some doubt on the other numbers)

  6. Aron
    September 13, 2010 at 9:34 am | Reply

    Also, a helmet will make you look less threatening and more easily overcome, if you happen to split up the wrong Asian family.

  7. jay
    September 13, 2010 at 10:26 am | Reply

    Robin, have you ever biked in the Netherlands? Many cities have bike lanes that are separated from the car lines with short concrete barriers. When I biked there I didn’t use a helmet either. Now that I live in Boston I refuse to bike entirely, helmet or no helmet.

  8. frank
    September 13, 2010 at 11:09 am | Reply

    Tim Harford had an article on the same topic a while back, one commenter, Tom MClaren, left this memorable comment:

    “Typical example of misuse of statistics. I can show you dents in my cycle helmet that would otherwise have been in my head. The details of this topic is not in the mean but in the tail – if you had an accident which involved a head trauma, would you rather be wearing a helmet or not? Stupid question, stupid debate.”

    • Vladimir M.
      September 13, 2010 at 3:36 pm | Reply

      And if there existed a significant population of people who wore helmets during their entire waking hours, there would be plenty of individuals who could show dents in their helmets incurred during walking, housework, showering, etc. By the standards of the quoted “memorable” comment, this counterfactual should convince you that wearing a helmet non-stop is worth the trouble.

    • jsalvatier
      September 15, 2010 at 10:47 am | Reply

      If the helmet didn’t need replacing, it probably didn’t prevent anything except a bruise.

  9. David Youngberg
    September 13, 2010 at 1:17 pm | Reply

    This seems like a clear cut case of the Peltzman effect. If you don’t have a helmet, you’ll take less care.

  10. Lo Statuz
    September 13, 2010 at 1:38 pm | Reply

    Even if a crash kills you, a helmet might protect your head enough that it would still be worth freezing.

  11. Vladimir M.
    September 13, 2010 at 3:49 pm | Reply

    There is clearly a prominent status-signaling issue here. In places like Denmark or Netherlands, using a bike as one’s everyday means of transport is a regular thing that normal respectable folks do. In North America, in contrast, it’s something that’s considered eccentric at best, and low-class at worst. Therefore, people instinctively reason that it’s only proper that individuals who do it should be made to bear prominent marks of their eccentricity and/or disrespectability.

    • Matt Simpson
      September 13, 2010 at 4:19 pm | Reply

      Therefore, people instinctively reason that it’s only proper that individuals who [ride bikes] should be made to bear prominent marks of their eccentricity and/or disrespectability.

      Isn’t the fact that they’re on a bike in an area where people either drive cars or walk already a prominent mark of their eccentricity?

  12. Gee
    September 13, 2010 at 4:07 pm | Reply

    More skeptical helmet sites …

    http://www.vehicularcyclist.com/hfaq.html
    http://www.cyclehelmets.org/1146.html

    More pro-helmet — located in Arlington, VA! — site

    http://www.bhsi.org/

    You did not mention the real possibility that helmets increase the likelihood of rotational injuries that rotational impacts/injuries have a much stronger relationship with brain injuries than direct impacts.

    For an excellent meta analysis and literature review see …

    The efficacy of bicycle helmets against brain injury , Accident and Prevention, March 2003.

    Fundamentally, a helmet probably does some positive things for straight impacts and slow riding generally associated with children. But a helmet is designed to protect a head from a standing two-meter fall. A little back of the envelope math should debunk the fantastic claims of protection from fatalities which almost always occur from a collision with an automobile. So I am in the camp that concludes helmet use is wildly over-emphasized such that many people equate cycling with a helmet with safe-cycling.

    BTW, before you think that cycling on the Custis, WOD, Mount Vernon and other local trails is “safer” — in quotes since it sort of depends on how one defines it — than road cycling there might be another vein of research to examine.

  13. Explodicle
    September 13, 2010 at 4:49 pm | Reply

    Since I trust physics more than statistics, I think that risk compensation is the culprit here, like with seat belts. I intend to keep wearing mine because I hit my head on things way more than the average person, and because I value my brain (relative to the rest of my body) more than the average person. It has already distributed what would have been a painful impact on a low-hanging branch.

  14. John Maxwell IV
    September 13, 2010 at 5:16 pm | Reply

    I think I’ll keep wearing my helmet, but only because my helmet-mounted mirror is nice.

  15. Reverend Twowheeler
    September 13, 2010 at 8:03 pm | Reply

    I think wearing a helmet however you travel is completely up to you. If I’m riding quickly down a mountain, then I think I’d want a helmet.

    That said, over-emphasis on helmets in cities is really counterproductive, given they don’t prevent car accidents happening and bunch of behavioral factors do. The number of headphones & helmets you see around Vancouver is scary, and I’ve yet to see a cop stop a helmeted cyclist and ticket them for their headphones.

    The problem with making it illegal for adults to cycle anywhere anyhow without a helmet is that a big demographic just won’t, and that’s the demographic you WANT to cycle for safer streets. Accidents basically happen when young men jump red lights, and in my opinion the best way to discourage that is get more moms cycling. Helmet laws encourage fewer, faster, more dangerous cyclists. There is safety in numbers and normalcy.

    I love these two threads on the Boris Bikes (the bike share scheme) forum in London about the civilizing effect of more, slower, normal people on bikes:

    “ok, what is with cyclists and red lights?”
    http://www.borisbikes.co.uk/topic.php?id=262#post-2168

    Making me a nicer person
    http://www.borisbikes.co.uk/topic.php?id=157#post-1127

    Note that I’ll happily endorse helmet laws for kids, just as I’m happy with drinking, driving, sex and voting laws for them. And I don’t buy example-setting as an adult-law justification for the same reasons.

    • Doug S.
      September 14, 2010 at 2:12 am | Reply

      Note that I’ll happily endorse helmet laws for kids, just as I’m happy with drinking, driving, sex and voting laws for them.

      That’s adultism, you insensitive clod! :P

  16. Matt Flipago
    September 13, 2010 at 9:13 pm | Reply

    Cyclist are often going a similar speed as a motorcycle, and yet, the bicyclist has basically no helmet at all. It does take much to look at a bicycle helmet and see that junk wouldn’t help you unless your a child who falls of his bike at 10 mph. To make safe helmets, you would have people actually stop cycling, because they would be so heavy.

  17. baakanit
    September 14, 2010 at 1:56 am | Reply

    I used to hate helmets, and didn’t find no use in them until, I rode on a slippery road and ended up hitting a fence. Without that helmet I don’t know what would have happen to my head. My cheeks were bruised and I ended up with seven stitches below my lips.

    Helmets are annoying, but its true value comes in those times that the unexpected happens.

  18. Robbie
    September 14, 2010 at 4:04 am | Reply

    Cycle lanes aren’t about helping cyclists:

  19. Robbie
    September 14, 2010 at 4:08 am | Reply

    The link that I embedded doesn’t seem to have worked.

    http://en.wikipedia.org/wiki/Bike_lanes

  20. MartinB
    September 14, 2010 at 7:01 am | Reply

    I used to use the helmet on longer trips, but not on shorter ones. Then I got my personal head injury while biking a 200meter distance between university buildings. A helmet or walking would have prevented it.

  21. arch1
    September 14, 2010 at 6:42 pm | Reply

    Yes this seems entirely consistent with they hypothesis that people spend less effort on risk aversion when the gain of doing so is reduced.

    And, since head injuries per accident went down significantly, it appears plausible that if you put on a helmet and do not yourselfbecome less risk averse, your chances of a head injury will go down significantly.

  22. Stephen
    September 15, 2010 at 6:15 pm | Reply

    The countries with the best cycle safety records (Denmark and the Netherlands) have among the lowest levels of helmet use. …
    … Despite the lack of helmets, cycling in the Netherlands is safer than in any other country.

    As anyone who has cycled in the Netherlands would know, most cyclists ride from A to B at an extremely leisurely speed, typically jogging speed. Even with excellent bike paths, there are many accidents (e.g. zero visibility when cycling with an umbrella in heavy rain; shopping bag caught in the front wheel; tourists crossing bike paths; skidding on ice/snow in winter; colliding with other cyclists when changing songs on your iPod; and [the cause of my own hospital visit] hitting a rubbish bin while cycling with an LCD TV). Few of these involve real injuries because speeds are low.

    Incidentally most helmets in Holland are worn by race cyclists. They definitely don’t want their heads hitting the road at 45 km/hr.

  23. Richard Tulloch
    September 16, 2010 at 12:12 am | Reply

    I ride regularly in both Holland and Australia, and do as in Rome in both countries. (Though I’m not sure what real Roman cyclists do – stay off the roads altogether I guess). In Sydney I’d feel vulnerable in a helmet; in Amsterdam I’d feel like a show-off wearing one.

    The debate in Australia goes on:

    http://richardtulloch.wordpress.com/2010/09/15/bike-helmets-an-on-again-off-again-argument/

  24. James
    September 19, 2010 at 10:59 pm | Reply

    The point is, should helmets be compulsory..
    Not, if you should wear them.. Personally, I feel safer with a helmet, but that does NOT mean they should be compulsory for everyone. The writer of this article correctly pointed out that when helmets were made compulsory cycling fell by 30%.

    Additionally compulsory helmet laws make bicycle hire schemes, and rickshaw services a nightmare. These potential pro cycling tourist activities suffer, and people see cycling as unsafe. Additionally, if Helmet law is the answer why then is the safest place to ride a bike the Netherlands, and Denmark, where helmet laws dont exist?

  25. Entwhistle
    September 20, 2010 at 10:12 pm | Reply

    Robin, this is an honest question: why don’t you wear a helmet while you’re walking? Presumably there’s some measurable possibility it would protect you from serious brain injury or death. And it seems that you value your own life more highly than most people do, given your interest in cryonics. I know why Idon’t wear a helmet — because I don’t take as strong an interest in preserving my life, and because I care whether people think I look silly. But I would think the calculus might be different for you.

  26. Tim Tyler
    September 21, 2010 at 8:30 am | Reply

    Re: “Ordinary cycling is not demonstrably more dangerous than walking or driving”

    Yes it is. It is at least three times as dangerous as driving by every common mentrc. Some statistics on the topic:

    http://en.wikipedia.org/wiki/Air_safety#Statistics

    • sean
      November 3, 2010 at 12:27 pm | Reply

      How do they come up with these numbers? Surely nobody counted my walk to the corner store this morning.. nor my ride to the bar last night. Flight miles, flight hours and flight trips are easily counted. Same with bus and train. Cars are harder, but at least there are odometer statistics through the motor vehicle departments or at a minimum some estimation via the insurance companies (not sure if they dip into that data or not). But how do they calculate the hours, km and trips spent on foot or cycling?

      I’m not trying to discount the data, just questioning how they find it. I feel like they are missing a lot of kms and trips for highly common and non-regulated modes of transportation.

  27. axa
    September 21, 2010 at 8:16 pm | Reply

    hey, i do donwhill MTB every weekend. i will never ride my bike without a helmet. it’s just plain stupid. i’m pretty sure helmets do not prevent accidents, but they’re the difference between laughing and being carried straight to the hospital after a fall.

    i think the problem is that there are two different kinds of people and neither one is able to recognize the opposite. the first group is the “boring” ones: riding fixies for commuting or leisure. they never overspeed or jump.

    the second group is the recreational and professional cyclists. going at 60 mph on a road bike during a race and not wearing a helmet is not good, jumping a 30 foot ramp in a mtb is also wrong.

    the problem with the first group is that they asumme that everybody is as “boring” and careful as them. that is why they endorse “NOT USING A HELMET”.

  28. Jordan
    September 26, 2010 at 2:01 am | Reply

    Basically with all the pro-helmetters on this one; people with helmets cycle more dangerously, that’s a concern, but it’s not really the helmet’s fault.

    But I didn’t post just because I want people to listen to my opinion so…

    The largest [study], covering eight million cyclist injuries over 15 years, showed no effect on serious injuries and a small but significant increase in risk of fatality. … The head injury rate in the US rose in this study by 40 % as helmet use rose from 18% to 50%. …

    This can be explained away extremely easily. Don’t know when this study occurred, but compared cycling technology over a 15 year gap at any point in the last 70 years and injury rates going up should be taken for granted: bikes have been getting lighter, faster, and nimbler at a steady and amazing rate, and the average cyclist speed is better than ever. That means more collisions and falls.

  29. Phil Goetz
    September 29, 2010 at 2:00 pm | Reply

    At some point you have to allow common sense as evidence. If you fall off your bike, all else being equal, you’re less likely to get a head injury if you are wearing a helmet. I don’t need studies to prove that. And if studies conclude the opposite, I will say the studies are wrong.

  30. Douglas Knight
    September 29, 2010 at 7:17 pm | Reply

    Phil, that’s causal decision theory! All else is not equal. As a very clear example, wearing a helmet causes drivers to give you less berth. (not that berth is terribly relevant to safety)

  31. wilson
    May 31, 2011 at 5:25 pm | Reply

    When riding on bike paths, helmets actually make it substantially more likely you’ll hit your head. Your instinct to duck your head into your shoulders will typically prevent a head impact, while the additional inches of helmet often mean the helmet will hit. The helmet also puts you more off-balance as you fall. I know several people who’ve hit their helmets after a fall while riding. They all testify to this by way of saying they’ll never ride without one again. I’ve never heard of anyone hitting their head without a helmet, despite the fact that most people I’ve known in my life didn’t use one, including each of these very people for most of their cycling lives. (After all, virtually no one used a helmet 20 years ago, so most people 40 and up spent most of their riding time without one.)

    Anecdotal, but there are reasons to believe this would be born out.

    One way to test some of the implications is to try wearing your bike helmet for 15-20 minutes before going cycling. You’ll hit your head on cabinets, your car door, sometimes in ways that are actually painful.

  32. Chris Pearce
    June 19, 2011 at 6:30 pm | Reply

    I was in an accident while cycling, and I took a direct impact to the head. If I wasn’t wearing my helmet, I’d be dead. You will never convince me that wearing helmets is pointless.

    • Andrew
      June 20, 2011 at 6:05 pm | Reply

      But everyone keeps missing the point of this article. It’s not whether you should wear a helmet, it’s whether it should be legally mandated. Two hugely different things. You shouldn’t run with scissors, but I don’t think it should be illegal.

      I have been a competitive cyclist for most of my life, and I would never race or train seriously without my helmet. But if I rode to the corner shops it’s a completely different story. As an Australian who now lives in NYC I think it’s fantastic how many people I see commuting to work everyday, doing their shopping etc using bicycles. And none of them wear helmets, contrasted with Australia where the number of commuting cyclists is actually pretty low. The majority of cyclists are higher-speed fitness cyclists.

      Every person who rides a bike to work is one less car that will potentially run a cyclist down. And it’s cars that cause the vast majority of injuries to cyclists.

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