but the issue that prompted my emails to the prof and caused me to seek out the study were a number of helmets that had not crushed but simply cracked.

A co-worker had fallen, broke his collar-bone and his helmet. Of course he claimed he could have been far more seriously injured had he not been wearing his helmet and showed me it as evidence. It had no visible compression at all. It had simply split apart.

This spring, a Vancouver city councilman was riding through a stop sign while failing to notice an oncoming car and was hit. He had a concussion and neck injuries but credited his survival to his helmet. He invites citizens to contact him via his blog and since he talked about his collision and helmet, I emailed him to ask if the helmet showed any signs of foam compression. He emailed back and said, there was abrasion to the rear plastic covering and the helmet had split cleanly into 5 pieces. There was no compression.

While I was researching a column on BCs helmet law I exchanged numerous emails with a former provincial politician who worked on it. He claimed his helmet had saved his life this past winter and offered it to me to see the damage that had been done to it. There were a number of pics offered and I again wanted to see if there was any compression of the foam, but there wasn't.

These 3 incidents in no way may be representative of the overall rate of cracking without compression, but it sure seems to me, as someone interested and following this issue for over 2 decades, that these reported situations have increased over the years. Cracking without compression has always happened, but it seems this has been happening more since designs have changed to allow large vents.

Helmets still have to pass the standards test and that means less foam deflecting/absorbing the same impact. That means the foam has to change and it seems the foam is more dense and more likely to split. The industry doesn't reveal the failure rates for these designs but the director of one of the leading facilities that tests helmets for certification says failure is common.

Having too much foam, or too soft foam can cause problem too, but it seems the newer designs have gone too far in their density and the fundamental point of a helmets ability to crush has been set aside to sell more appealing designs.

If these helmets break more easily, it may even work to create the impression that the helmet worked, even if it is obvious that it didn't.

*Ooops, I almost forgot the point of my post. You mentioned,

"those who should know on a professional basis seem to think that helmets work as designed"

Well, after these 3 incidents, I emailed Bell and asked about the helmets that broke without compression. I mentioned their own site says helmets work through foam compression.

They replied that the helmets worked as designed, as they were supposed to, and that cracking is a valid way for EPS to attenuate energy.

This response just does not jive with what I've found elsewhere. You'd think Bell would understand how helmets work and saying cracking is a valid way to attenuate energy is more than a little misleading and ridiculous, if not irresponsible.