The New Standard
The most significant difference between SA2005 and SA2010 revolves around how Snell conducts the impact testing of the helmets. And one major criteria the Foundation adopted was to demand that less force be transmitted to the head during an impact, from 300 g's to 275 g's or less.

However, there are also some straight forward changes which we'll tackle first. In the labeling department, all helmets must be marked with the largest and smallest appropriate head circumferences in centimeters. This is a departure from the sizing structure of S, M, L, and so on that some manufacturers typically use.

The second change involves the samples used for testing. Depending on the helmet's intended size range Snell may ask the manufacturer to provide up to eight samples for certification testing. This ensures more uniform results across the test sample.

Finally, there are provisional testing and separate "SAH2010" or "KH2010" certification labels for head-restraint-ready helmets, which we'll get into a little bit later. If a model is not head-restraint-ready, this provision won't apply, but the model may still be considered for SA2010 or K2010 certification.

With the simple changes out of the way, let's dive into the most important change.

Impact Test Differences
The differences between SA2010 and SA2005 all stem from a reevaluation of impact test head forms. SA2005 and previous standards required impact testing on head forms with an effective mass of 5.00 kg regardless of head form circumference. In other words, the previous standard assumed that everybody's head weighed 5 kg or about 11 pounds.

This reevaluation of head form mass is supported by a study conducted at the University of Washington by Dr. Randal Ching. Dr. Ching performed measurements on 15 cadaver heads and found a strong correlation between head mass and circumference. This correlation approximates a cubic mass versus circumference relationship and suggests that the ECE 22-05 (the current mandatory motorcycle helmet standard throughout Europe) mass specification would enable a more precise fit between the properties of Snell-certified helmets and the needs of their wearers across a broad range of different head sizes. Translation? The bigger your head is the more it weighs. Makes sense, doesn't it?

In order to accommodate the new specification Snell had to change both the test procedure and the test criteria. In SA2005, if a helmet met requirements on a larger head form, the same helmet would obtain comparable results on smaller head forms. Not so for SA2010, each test criteria (head form mass, g-level test, and more) are correlated to each other. As you can see in Chart 1 a new head form designation "C" has been added between A and E.

In this same chart you can see how the drop mass (head form mass) changes in regards to the head form circumference. The certification test criteria for the medium and smaller sizes, head forms A through J, are all set to 275 g. The value comes directly from ECE 22-05. But this 275 g value, combined with the head form mass changes, would allow larger helmets to transmit more shock than allowed by SA2005. So, for the M and O head forms, the largest sizes, the peak G levels have been reduced even further to assure that SA2010 never allows any more shock than the Foundation allowed previously. The bottom line is that SA2010 helmets will absorb more impact.

The certification velocities replace the impact energy requirements of previous Snell standards. The energy requirements in SA2005 effectively demanded impact velocities of approximately 7.75 m/sec followed by 6.62 m/sec. However, the different impact masses must necessarily impose progressively greater levels of stress within the helmet structure as head form mass increases. Therefore, smaller sized helmets will be able to satisfy the test criteria in SA2010 at higher impact velocity levels than larger helmets. Since, like previous Snell standards, SA2010 will call out double impacts, the first certification impact will be at 7.75 m/sec regardless of head form size. The second impacts for the A, C, and E head forms are set to 7.09 m/sec but are set progressively lower for the J through O head forms to allow for the limits of current materials and design technology.