[email protected] wrote:
>
> Ok, I am now convinced that as a public health measure compulsory
> helmet laws and safety campaigns are not all they've cracked up to be...
> But what about performance in actual crashes? Pointers to info on this?
Let's think about how this could be determined.
You can't have people perform crashes with and without helmets. Not
only would it be ethically sketchy, you can't duplicate a crash. Bike
crashes are infinitely more chaotic than car crashes. This is because
the mass of the system is so low, and the number of degrees of freedom
of an unrestrained human body are so high, and the effect of muscle
contractions (volunary or not) are so large.
For the same reasons, using crash test dummies on bikes won't work.
Case-control studies are notoriously bad. The problem is, there is no
"control." People who have put helmets on are bound to behave
differently than those who have not, in many unpredictable ways.
What we need is to get rid of the large variations in individual
crashes, by averaging things mathematically. For that, we'll need a
large number of data points. How can we get lots of data on people
crashing with and without helmets, where the people are "the same
type"? That is, not comparing gonzo downhillers with mom's on bike
paths?
One way - perhaps the only way - is to look at a large population of
all types of cyclists, during a time when few of them wear helmets,
then compare to a time when that same population has most of the people
in helmets. See how many head injuries there are per thousand cyclists
in, say, one year.
One way - perhaps the only way - to arrange for a sudden change in
helmet wearing is to force people to suddenly start wearing helmets.
They won't do it in mass unless there's an enforced law on the books,
or maybe soon to be on the books. If you can find such a situation, it
can be a good "before - after" test.
And of course, this has been done. It's specifically this type of
study that shows the least benefit for helmets. In fact, the latest
such study showed negative benefit.
Keep in mind, bike helmets are designed, tested and certified for a
laughably low standard. This is necessary because a really strong
helmet would be unbearable on a bicycle. Helmet proponents never let
on how weak the standard is - but the entire point of Thompson &
Rivara's 1989 paper was to prove that yes, by golly, these super-flimsy
helmets really do work. It wasn't stated that way, and the study was
notoriously faulty, but that was the point.
What real-world, before-after data seems to show is that a helmet
designed, tested and certified for low level collisions actually works
only in low level collisions.
- Frank Krygowski