When Asphalt Attacks
Sam Fleming, Roadracing World & Motorcycle Technology
Published: July 01, 2002
This article first appeared in the July 2002 issue of Roadracing World & Motorcycle Technology.
There are many good reasons why you should not read this story and/or ignore everything presented below. I point this out now to save folks the trouble of writing in letters complaining about how this study is biased in one direction or another.
Bias in studies is always a problem; a problem which statistics can only go so far to alleviate. The method in which data is collected can skew results. And self-selected populations can create bias in the very population you are trying to study.
We collected data for this study by tapping into the vast ocean of road racers who read roadracingworld.com. We placed a form on the website which encouraged people to report up to 10 accidents which involved hitting their head. We asked the following questions:
We choose those questions to allow for a gradient of head injury within a "yes or no" context. One of the big challenges of psychometric scales (psychometrics are the quantification of behaviorÖi.e. "I hurt, on a scale of 1-10, a 3") is rigidly defining what each number means. There are all sorts of problems if a 7 on a scale means one thing to one person and something else to someone else. We tried to avoid this problem completely by not having any questions with scales. We stuck with simple yes or no questions.
We do have a self-selected population. We could not force people to answer the survey so only people who could answer the survey and were willing to answer the survey are included in these results. This approach excludes a crucial group of helmet users: People who died from head injuries while wearing helmets. Not to be overly grim but our study does not include fatalities since those people could not respond to the survey. That said, although I do not pretend to be intimately familiar with every racetrack fatality in the country, the ones that I know of that involved head injury were catastrophic and it is hard to believe that any helmet would have prevented death.
It is also possible that people who use the Internet crash in a different manner than people who do not use the Internet. Or that roadracingworld.com readers crash harder than non-roadracingworld.com racers. There are many such lurking variables that cannot be controlled for and cannot be quantified in the numbers.
This study resulted from my own personal curiosity about crashes. After being around the sport for 13 years I have seen people crash for years and then have one big hit that disturbs their inner balance and forces retirement. I have seen people who are barely intelligible for a few hours or days and then regain complete function. I have seen people die from what would appear to be a minor get-off and folks walk away from horrendous accidents.
Crash helmets are designed to cut wind noise and protect your eyes but, primarily, they are designed to slow down the impact when your head is moving and hits something stationary. The math of this stuff is terrifying. Just a minor fall from a moderate height can produce shock loads far higher than you would think. Picture jumping off a bridge attached by the waist to a 20-foot steel cable. When you hit the end of that cable you will either be cut in half or your back will break. Attached to a 20-foot stretchy rock-climbing rope you will slowly decelerate and barely feel a thing. Helmets are supposed to do the same thing. They are supposed to decelerate your head into the pavement at a survivable rate. The helmet hits the pavement and stops abruptly. Your skull goes into the foam liner and decelerates at a slower rate. Your brain then gets squished into your skull at an even slower rate. Because the liner (and or shell) tends to get crushed it is highly recommended that you replace your helmet after any hit.
There is also the whole discussion about hard helmets and soft helmets. For a given size and weight a helmet can be designed to reduce brain injury (which is caused by your brain sloshing around in your skull, either twisting or compressing) for a minor impact or a major impact. The challenge is, if you design a helmet (again, for a given weight and size) for the big crash, you might have to make the helmet so strong that minor crashes transfer more energy into the brain, causing more damage than if you had designed the helmet for a minor or moderate crash. Big crashes are rare. Moderate crashes are more frequent. Brain injuries can be cumulative. So, lots of minor hits in a hard helmet could add up to something permanent, but then, the big crash might be survivable in a hard helmet while it might have been fatal in a helmet designed for minor or moderate impacts. This is all theory since motorcycle helmet manufacturers do not typically advertise their helmets as being harder or softer but usually talk more about paint schemes or ventilation.
Then there is the question of reviewing helmets. In an ideal world you would subject identical groups of people to identical impacts wearing different helmets and measure the results. Besides being unethical (which, of course, didnít stop the Nazis from freezing people to death, amongst other things, in the name of research), it would be very difficult to perform such a study.
So, we did the next best thing. We took over 2000 people who had crashed multiple times and asked them how they fared. We know the people are different, we know each crash is unique. We are assuming that the law of big numbers is averaging all of these things out. For instance, it is unlikely (although possible) that Shoei owners crash lighter or harder than Bell or Arai helmet owners. It is far more likely that there is a distribution of crashes from light to hard in each owner group and that those distributions of crashes should be about the same.
Since there is no way to quantify the severity of a crash, we didnít attempt to. As a surrogate for crash severity we asked people if they retired the helmet after the accident. Retiring the helmet was our digital measure (yes/no) for the person having hit their head with some severity. Because racers are a cheap bunch, we also gave them the option of noting that they should have replaced the helmet, even if they didnít.
We took care to avoid ballot stuffing by requiring e-mail addresses be supplied with each response. We used the e-mail addresses to verify the validity of each submission and tossed the ones that were duplicates or from bad addresses. There were surprisingly few such cases.
The last step we did was to eliminate any accident that was more than five years ago and we eliminated responses where the respondent had not hit their head hard enough to require the retirement of the helmet. The survey being, after all, about helmets. This did not eliminate many responses which suggests that people were really only filling out the survey for accidents in which they did hit their head pretty hard. What we were left with were 1295 accidents involving 858 riders.
We ran the statistics on the entire dataset and then again on the reduced dataset. The accident data also corresponds to the approximate market representation in the industry. We saw that Bell helmets used to have much more of the market than they do now. Bell representation in the industry seems to have dropped from 4.3% to 1.7%. Arai seems to have been extending its lead in terms of helmet use as well. This first chart simply shows the counts of the helmets in the accidents and the relative percentages of the various manufacturers.
The next chart looks at the number of accidents with a head hit hard enough to have the rider retire the helmet (or indicating that they should have retired the helmet) compared to the number of respondents that indicated symptoms consistent with a concussion.
Brands with small populations do not really have enough of a sample to draw conclusions. I would suggest disregarding the results for any of the manufactures with a count less than 50. For the brands with larger sample numbers we find that the results are very consistent, ranging from a low of 32% (Arai) to a high of 36% (HJC) of crashes producing concussion symptoms. These differences are so slight they can probably be chalked up to noise in the data.
It is probably not surprising that the results are as consistent as they are due to the standards to which all the manufacturers conform their product. The surprise to us was, not that the results across the brands were consistent, but that fully 1/3 of all big hits resulted in a concussion. Granted, most of these people would have died had they not been wearing helmets but it was a surprisingly high percentage of riders who hit their heads and suffered injury. Perhaps this relatively high injury rate indicates a need for Snell, DOT and BSI to rethink their standards for motorcycle helmets.
Four views of a helmet from a crash in turn nine at Willow Springs that saw the rider land with the bike on his head. The result was a concussion from which full recovery took months.
All helmet manufacturers recommend the replacement of any helmet after an impact. Some provide a free inspection service where they will inspect the helmet and return it to you if the helmet is still capable of providing protection. We requested inspection information from each manufacturer but only heard back from four:
Free Inspection Service, With $10 Return Shipping Fee.
P.O. Box 9485
Daytona, FL 32120
Free Inspection Service
Call Lee Jason at (714) 670-0419 to arrange an inspection.
Free Inspection Service.
Inspection takes up to three days and the helmet is returned via UPS ground with a letter of explanation and recommendation.
Shoei Safety Helmet Corp.
3002 Dow Ave. Suite 128
Tustin, CA 92780
Free Inspection Service.
(950) Gilman St. Suite 800
Berkeley, CA 94710
In all cases, include your name, return address, daytime phone number and a brief description of what happened to the helmet.
In the past magazine reviews of helmets have been largely limited to liner comfort, wind noise and color. The above results suggest that any of the major brands offer comparable protection and that price, comfort, wind noise and color are a perfectly acceptable criteria.
And that the best strategy for limiting head injuries is to avoid falling down.
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