How many helmetless cyclists do not survive just fine though compared to the 450 that do?

Regardless of what impacts the helmet they are designed to take so much of an impact to HELP protect a persons head. If the impact, regardless of if it comes from a moving or non moving motor vehicle or a paved or non paved area of the ground, exceeds a helmet's design specs. then yes a helmet will fail at that point to protect & serious injury or death could occur. On the inside of both motorcycle & bicycle helmets there is a sticker that plainly states "helmet will not protect from all impacts". But wearing one is still better then not, with one on you your head at least has some protection against an impact. With out a helmet statistics have proven even a light impact to the head can seriously injure or kill a person.

As is the case with this woman who had an accident with a police car. Granted it is not clear what her head impacted, the ground or the cop car. Obviously the helmet helped prevent serious injury or even death.

Though I do not know right now I have a hunch there are more light to medium impacts to the head in the event of a bike accident that bike helmets protect against then hard or heavy impacts. I also do not know what could be considered a light or medium compared to a heavy impact. I'm guessing a lot of factors are involved like speed of the cyclist, speed of other vehicle if one is involved, type of surface cyclist is imacting with, etc.

I do know from personal experience when I have had an accident where my head impacted something what was impacted was the ground in most cases, in one case it was a steel pole, I was the only one moving & the impacts were what I would call light to medium. Had I not been wearing a helmet the accident would have resulted in serious injury & in 2 of the cases death.