I am in favor of bicycles, bicycling and bicycle safety. I am opposed to bicyclists sustaining injuries and particularly head injuries that result in traumatic brain injury. More bicycles on streets and roadways make all bicyclists safer. Mandatory helmet
laws increase the rate of helmet use but decrease the number of bicyclists. The
health benefits of riding a bicycle far outweigh the risks of injury or death
(in “life years”). Bicycle helmets represent a design compromise that reduces
effectiveness in a crash in favor of lighter weight, comfort and ventilation.
If you are relying on a helmet to keep you safer while riding a bicycle, you
have skipped a number of important steps that can more effectively keep you “safer.”
I ordinarily keep my opinions about bicycle helmets to myself. I never tell anyone not to wear a helmet, though I sometimes wish the helmet people would reciprocate. The only reason I’m going “public” now is because the Active Transportation Alliance has
adopted a policy of making helmet use mandatory for its various fundraising
and/or sponsored events. The language currently being used is “I agree to wear a helmet suitable for cycling at all times during the bicycle tour. Those who refuse to
wear a helmet will not be permitted to ride and will not receive a
refund.” The attorney side of me suspects this is an insurance underwriting requirement and the ATA needs to include this language to get a break on its liability premium (or possibly, a requirement to get any kind of coverage at all). And lest any of you think that the insurance underwriters are trying to make everyone safer, additional
requirements imposed on the policyholder are typically included in policies to
form a basis for excluding coverage.
The bicyclist side of me is disappointed that an organization which professes
to “advocate for transportation that encourages and promotes safety, physical activity,
health, recreation, social interaction, equity, environmental stewardship and
resource conservation,” has adopted a policy which runs contrary to that
mission statement. (I just became aware that “Bicycle Chicago Meet-up” and
Lee’s Big Shoulders Neighborhood Tours have the same requirement.)
I don’t want this post to be about me, but by way of background, my bicycling “experience” pre-dates the widespread use of helmets
(probably even the old “hairnets”). When I was a kid, you wore a helmet when you played football and when you batted in baseball, but that was pretty much it. In high school
and college, I competed in gymnastics (trampoline, no less), rugby and ski
racing - never wore a helmet, and neither did anyone else. My non-competitive
unhelmeted activities during this period of time included freestyle skiing with
lots of inverted aerials, and lots of vertical mogul runs. Bicycled some in
college, but never wore a helmet. Always wear a helmet snowmobiling, but
seriously, that’s a little like requiring people to wear a helmet when they go
skydiving. How did people survive such ultra-hazardous activities in the
pre-helmet dark ages? We took extra care not to hit our heads when we fell
down. Sometimes the old ways are the best ways.
This is not an academic paper for peer review, so I’m going to omit cites. If you’re really curious about one of them that you can’t find yourself or feel the need to rip on me in general, let me know and I’ll try to find it again. I know there are a lot of engineers and health care professionals on the chainlink, and I hope this post yields some constructive
criticism and feedback.
Bicycle helmets are mostly designed for slow, vertical falls. The testing methodology is to drop the weighted (11 lbs/5 kilos) helmet from a height of 1.2 meters onto a round anvil and/or a curb-shaped anvil and from a height of 2 meters onto a flat anvil. The headform measures the amount of impact attenuation when the helmet comes to rest, expressed in joules. A helmet which “passes the test” can permit a maximum of 98 joules at the headform. Failure threshold is 300 g, which happens to be the level at which you can expect to lose consciousness, and probably suffer some injury which hopefully will not be permanent.
Real world impacts are going to look a lot different from the testing methodology in that they are much more likely to include: multiple impacts, irregularly shaped “anvils,” and rotational forces (think crack the whip or water skiing outside of the wake when the boat turns). Real world impacts are also much more likely to occur with some significant horizontal speed (which has both advantages and disadvantages).
I bought my first helmet in about 1988. It was a thick styrofoam, poorly vented Specialized helmet which had a nylon fabric cover stretched over it and bore certification stickers to the 1984 Snell and ANSI standards. The unfinished styrofoam design was abandoned within five years for the hard shell finish due to the observation of increased neck and brain injury related to rotational forces exerted upon a helmet which was too “grippy” when it contacted pavement.
Bicycle helmet design must strike a balance between fashion and function. As the pressure has built for manufacturers to design “cooler” helmets (both from an aesthetic and ventilation standpoint), more and larger vents have been cut into the helmet surface. This has resulted in helmets which are indeed cooler and lighter, but which lack the structural integrity of my ugly old Specialized helmet. And penetration risk from rocks and tree branches when mountain biking?: Forget it; not even tested anymore; too many vents. Snell standards are gone, the certifying bodies in the U.S. are now CPSC and ASTM both of which require less energy attenuation than the Snell 95 standards
did. If you’re really serious about wearing a helmet to protect yourself from
traumatic brain injury, buy yourself a good, full-faced Arai, Bell or Shoei
motorcycle helmet-much better energy attenuation, and you also get the added
benefit of protection from facial injuries.
I wear a helmet approximately 25% of the time I ride a bike. My decision to wear a helmet is usually based on: a) likelihood of sustained speeds in excess of 18 mph; b) exceedingly long rides (>6 hours); and/or c) riding with a lot of strangers. I ALWAYS wear a helmet when I ride a mountain bike on trails. The only time I have ever hit my head when bicycling was when I was wearing a helmet. It’s not that I’m such a genius at predicting crashes, it’s simply because a helmet adds an additional 2-3 inches to the
radius of my head and that confuses my muscles and my sensory nervous system. I
have spent a lifetime “learning” where the perimeter of my head ends and I
can’t rewire my perceptual system to account for that extra 2-3 inches. I have
never been hit by a car, but I’m not counting being doored three times over the
Fear is a very effective marketing tool. Whether you’re Rahm Emanuel not wanting to let a good crisis go to waste, or you’re the Bush administration trying to head off the impending invasion of the U.S. by Islamic extremists, a lot of things get “sold” in this country based on an inflated perception of danger. Bike accidents result in approximately 540,000 emergency room visits in the U.S. every year. Of those, 67,000 (12.4%) involve head injuries, and 8375 involve brain injuries [TBI] (1.5%). I can’t find the exact cite for this one folks, but it’s fairly representative of any given year in
the U.S. I’m going to make a pure guess that emergency room visits as an
accident index result in underreporting the total number of bicycle accidents
by a minimum of a factor of three; i.e. there are 3 times as many bicycle
accidents in the U.S. each year and that for every one that sends someone to
the emergency room, another two go unreported or at least don’t result in a
trip to the hospital. I’m also going to guess that an accident serious enough
to result in a TBI is unlikely to result in no hospital visit, so the 8375 TBI
number is probably pretty close to accurate. If this data and these guesses are
true, your risk of TBI is about 0.5% for any given accident, and probably even
lower than that.
Riding a bicycle can improve cardiovascular fitness and improve Body Mass Index, but it doesn’t change certain hard-wired physiological traits or cognitive functions that assist in making you a “safer” bicyclist. We all have differences in strength (including the composition of slow-twitch vs. fast-twitch muscles), balance, visual acuity, (including depth perception and ability to detect motion), hearing, proprioception, and judgment, to name just a few. I have seen at least a half a dozen bicyclists in the past week, after dark, wearing a helmet, with no lights on the front or the back of their bicycle. I have told two of them they’re going to need a bigger helmet.
As stated, I am opposed to head injuries and particularly traumatic brain injuries. My brain has remained a solid second on my list of favorite organs since adolescence. If I’m ever in a bicycle accident with a car, I want to be dressed like the guy in “The Hurt Locker.” Most studies of the efficacy of bicycle helmets have found them to be effective at reducing the risk of head injury. In my estimation, that takes the risk down from remote to infinitesimal.
Mandatory helmet laws increase the rate of helmet use, but reduce the number of cyclists on the road (Australia, New Zealand, Canada - British Columbia and Nova Scotia).
More cyclists on the road make all cyclists safer. In 1994, 796 bicyclists were killed in crashes with motor vehicles; in 2009, 630 bicyclists were killed in crashes with motor vehicles (-21%). Trips by bicycle have increased from 0.7% in 1990 to 1.0% in 2009 (+43%).
Portland reported this year that their rate of helmet wearing has increased to 80%, all through promotions and peer pressure. I have no problem with encouraging people
to wear helmets, strongly recommending that people wear helmets, but REQUIRING,
and EXCLUDING? Can’t we all just get along?