Boni, Arthur ([EMAIL PROTECTED]) writes:
.... snip ...
> If I may state my own opinion, however - and an obvious lesson from this
> accident - Brian would have undoubtably suffered a serious, if not fatal,
> head injury had he not been wearing a helmet. His helmet was cracked in
> half!
Without getting into the minefield of bicycle helmet use or even trying to
guess the merits of this specific case, I'd just like to avoid the creation
of our own mythology.
A crack in a helmet is not a valid indicator of the degree of protection
afforded by a helmet. It takes very little force to crack a helmet. I've
seen one crack when dropped from a height of less than one metre. In
accident/injury reconstruction involving a helmet, compression of the foam
liner is measured. From this, an estimate of the G force absorbed from the
impact is derived. The foam is plastic and once crushed stays crushed. If
the liner has been compressed to its original, and thus minimum, thickness
(i.e. before it was "foamed" in the manufacturing process), the impact will
have exceeded the helmet's certified protective value of 300g's (or the rough
equivalent of the vertical force of an impact with the ground from a
cyclist falling off a bicycle). Anything in between "no crushing" and
"complete crushing" means the helmet absorbed some energy but the equivalent
of something less than that generated by falling from the height of a bicycle.
The amount of energy can only be estimated by first examining the helmet in
a lab.
In most cases including this one, the obvious lesson is the avoidance of
an accident in the first place.
Please, let us not forget the number 1, 2 and 3 injury prevention measures -
skills, skills, and more skills. Their relevance is even greater given the
close proximity of other cyclists when we are riding in a pack. As it was,
another cyclist was taken down in this incident. Fortunately he escaped
uninjured.
--
Avery Burdett
Ottawa, Ontario
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