Motorcyclist mag takes credit for new Snell test
Motorcyclist magazine takes credit for an "improved" Snell standard in their article "Snell sees it our way." I did not see it their way, so this is the note I sent:
In your article "Snell sees it our way," you take credit for what you view as improvements to the Snell standard. However, there are criteria, other than the peak G limit and head form sizes, in the Snell and ECE 22-05 testing standards that affect how a given helmet will perform.
For example, the Snell 2010 standard imposes two strikes whereas ECE is a single strike test. The two strike test requires helmets to manage much higher levels of impact energy than the single strike test. Another significant difference is that ECE includes Head Injury Criterion (HIC), which introduces a time duration factor into the evaluation. As you noted in "Blowing the lid off" with respect to the DOT 400 G limit (effective limit of 250g), a time duration requirement effectively lowers the peak G limit. Snell has no such time duration requirement. The double strike and HIC factors are likely to cause helmets to perform differently on the peak G limit test, event though the two tests have the same peak G limit. I expect ECE (and DOT only) helmets to continue to produce lower peak G force test results than helmets built to the Snell 2010 standard.
Regarding the Snell 2010 double hits, you previously criticized this requirement in "Blowing the lid off," as major factor of the Snell test leading to helmets that are too stiff and thereby less safe. You reported that the 2010 standard brings Snell more in line with the ECE 22-05 standard, but as previously mentioned the ECE standard does not require double hits.
Also, the second hit required by the 2010 test is higher for some head forms than mandated by the Snell 2005 criteria. Snell M2005 requires a first hit of 7.75 meters/second (or 150 Joule impact) and a 6.6 m/s (or 110J) impact for the second strike. Under the 2010 requirements the first impact criterion remains the same but the second impact has been increased for head forms ISO A, C, E, and J. It is welcome revision that the 2010 revisions take into consideration head size, but the more stringent requirements for the second impact for most head form sizes is likely to offset much of the potential benefit. The increase in the second impact velocities may contribute to helmets being even more resilient (not less-rigid as you said) causing energy to be absorbed efficiently only at values of head injury criterion well above those which are survivable.
Snell helmets could become more rigid as a result of the increased second impact velocities and still pass a lower peak G limit because many Snell helmets pass the Snell peak G limit with room to spare. The complicating factor for Snell rated helmets is that they also have to deal with the DOT peak G limit, at least here in the states. Hopefully the DOT limit will keep peak G force limits in check, but if excessive G forces are kept down it will not be due to the Snell standard.
So, I wouldn't pat myself on the back and take credit for an "improved" Snell standard if I were you. What riders need is a testing standard that promotes the production of helmets that will protect us from fatal injuries, as well as offering more protection from non-fatal brain injuries. The Snell 2010 standard does not appear to be a step in that direction.
Motorcyclist magazine takes credit for an "improved" Snell standard in their article "Snell sees it our way." I did not see it their way, so this is the note I sent:
In your article "Snell sees it our way," you take credit for what you view as improvements to the Snell standard. However, there are criteria, other than the peak G limit and head form sizes, in the Snell and ECE 22-05 testing standards that affect how a given helmet will perform.
For example, the Snell 2010 standard imposes two strikes whereas ECE is a single strike test. The two strike test requires helmets to manage much higher levels of impact energy than the single strike test. Another significant difference is that ECE includes Head Injury Criterion (HIC), which introduces a time duration factor into the evaluation. As you noted in "Blowing the lid off" with respect to the DOT 400 G limit (effective limit of 250g), a time duration requirement effectively lowers the peak G limit. Snell has no such time duration requirement. The double strike and HIC factors are likely to cause helmets to perform differently on the peak G limit test, event though the two tests have the same peak G limit. I expect ECE (and DOT only) helmets to continue to produce lower peak G force test results than helmets built to the Snell 2010 standard.
Regarding the Snell 2010 double hits, you previously criticized this requirement in "Blowing the lid off," as major factor of the Snell test leading to helmets that are too stiff and thereby less safe. You reported that the 2010 standard brings Snell more in line with the ECE 22-05 standard, but as previously mentioned the ECE standard does not require double hits.
Also, the second hit required by the 2010 test is higher for some head forms than mandated by the Snell 2005 criteria. Snell M2005 requires a first hit of 7.75 meters/second (or 150 Joule impact) and a 6.6 m/s (or 110J) impact for the second strike. Under the 2010 requirements the first impact criterion remains the same but the second impact has been increased for head forms ISO A, C, E, and J. It is welcome revision that the 2010 revisions take into consideration head size, but the more stringent requirements for the second impact for most head form sizes is likely to offset much of the potential benefit. The increase in the second impact velocities may contribute to helmets being even more resilient (not less-rigid as you said) causing energy to be absorbed efficiently only at values of head injury criterion well above those which are survivable.
Snell helmets could become more rigid as a result of the increased second impact velocities and still pass a lower peak G limit because many Snell helmets pass the Snell peak G limit with room to spare. The complicating factor for Snell rated helmets is that they also have to deal with the DOT peak G limit, at least here in the states. Hopefully the DOT limit will keep peak G force limits in check, but if excessive G forces are kept down it will not be due to the Snell standard.
So, I wouldn't pat myself on the back and take credit for an "improved" Snell standard if I were you. What riders need is a testing standard that promotes the production of helmets that will protect us from fatal injuries, as well as offering more protection from non-fatal brain injuries. The Snell 2010 standard does not appear to be a step in that direction.