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.
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%).
Ain't statistics grand?
Brendan Kevenides said:Thanks, Kevin.
Interesting. A 2010 Canadian study in the report you provided from the Bicycle Helmet Safety Institute concluded, "Canadian youth and adults are significantly more likely to wear helmets as the comprehensiveness of helmet legislation increases. Helmet legislation is not associated with changes in ridership.." There are other studies referenced that either demonstrated or speculated that mandatory helmet laws do or could reduce the number of cyclists. However, a smallish reduction in ridership is, in my view, overwhelmed by the down right spectacular reduction in deaths, especially among children, seen pretty much everywhere when helmets became mandatory.
I took the following from the report: (1) Mandatory helmet laws greatly increase helmet use, especially among children; (2) Wearing a helmet dramatically reduces your chances of death in a bike accident; and (3) It is not clear that mandatory helmet laws reduce ridership. According to a study published this year, it does not.
Kevin Conway said:Yup. Courtesy of the aptly named Bicycle Helmet Safety Institute.
Here's a link to articles specifically dealing with Western Australia.
Brendan Kevenides said:"Mandatory helmet laws increase the rate of helmet use, but reduce the number of cyclists on the road." Kevin do you have a citation for this?
I think I am for mandatory helmet laws. (I could perhaps be talked down from this position.)
Thanks for this interesting post Kevin.
damn americans and your right to choose...
Correlation does not imply causation... and if you are going to quote statistical data you will need to link to the sources.
Strong consistent correlation between two events is can be taken as causation between the two events or a common underlying cause. That's as good as it gets even in the hard sciences.
I have never been an "ALWAYS" bicycle helmet wearer, but I just may have been converted.
Heading back to Union station last night after CM, I took a spill I never saw coming. Before I knew it, I was face planted on the concrete.
Forget having time to "fall correctly", I spent all my head-first-into-the-pavement time trying to figure out why my front wheel sunk right into the road! Did I miss a hole? Did my wheel collapse?
Luckly, I had my hemlet on, and the helmet and my chin took pretty good hits. My chin didn't fare as well as the helmet, which did great! (see pics below)
Got up quick, had to find out what happened. I had just ridden into freshly poured concrete. Amazing how fast that will swallow up a wheel and toss you.
True, there were lots of clues I should noticed about the fresh concrete, but at the time, I never expected it.
You just never know.