Originally Posted by Allister
The idea that a helmet crushes to help reduces deceleration forces is a persuasive one, but I've yet to see or hear about a helmet that actually does this. It's a myth. Stop believeing the propaganda. To do this the material deeds to be a lot more deformable than the stuff they currently use.
The Snell Foundation created a very tough certification program for bike helmets. They developed sophisticated tests to measure exactly how well helmets protect the brain from deceleration forces. The Snell certificate required testing of prototypes, and then actual production models. Snell would then go to stores, and buy random samples and test those as well.
Snell charged manufacturers a hefty fee to recover the costs of their extensive testing program. After the CPSC stickers became "standard", most manufacturers in the USA dropped out of the Snell testing program. The manufacturers figured (correctly) that a typical LBS and typical helmet buyer would assume that the CPSC sticker means the helmet meets a high standard for protection against brain injuries.
I wish some Bill Gates kind of guy would give the Snell Foundation enough money to test all of the "best selling" helmets. I'm kinda suspecting that there are some helmets with CPSC stickers that would not pass the Snell tests - but it would cost big bucks to find out.