Originally Posted by
CrankyOne
Foam bicycle helmets are only effective within a very narrow range of impact angles, velocities, and struck object shapes. Outside of these or when not fitted properly and tightly against the head they are ineffective. The purpose of the helmet is for the foam to compress and so lessen the sudden deceleration of an impact (to keep your brain from compressing up against your skull to hard). If it is not tightly against the head on impact then it cannot do this. Similarly, if the helmet cracks instead of compressing then it is not effective beyond reducing abrasions.
This is likely what explains why head injury rates (TBI as percent of all injury types) are the same in helmet wearing countries (USA, CAN, AUS, GBR) as in countries such as The Netherlands where nobody wears them and why there has not been a decline when mandatory helmet laws have been enacted such as in AUS.
Impressive that you fit The Netherlands into this discussion. Your ability to compare/contrast the US and The Netherlands is second to none.
You dont mention another extremely legitimate benefit for helmets. Falls, while perhaps not creating severe brain injuries, can scrape your scalp, ear, and face if no helmet is being worn.
Sliding on your ear for 15' or helmet for 15'...which is better?
And reducing abrasion injuries to the face and head are a real benefit, not some debatable benefit that a handful of resistant cyclists will argue to the pain.