More Info on helmets

Cliff said:

Well if you think that helmets don't reduce head injuries, then I suppose it
is best that you keep burying them in the sand.

And if you actually have good evidence that they prevent serious head
injuries [1] then you must be the only one on the planet...

...d

[1] Not scratches and bruises but concussions, subdural haemorrhage or
the like..

in message <[email hidden]>, Al C-F

(') said:

Simon Brooke said:

If the RoSPA are right, how do you account for the fact that across
the world there is a strong positive correlation between helmet
wearing rates and cyclist injury rates.

A correlation, as you rightly say...

Quoted message said:

In the
real world, helmets really do kill more people than they save.

...that you are taking to imply causality.

It's causal, whichever way you look at it. If, as has been argued,
increasing helmet use deters people from cycling thus decreasing
cyclist numbers[1], and the decrease in numbers leads to an increase in
the kill ratio, that's caused (indirectly) by helmet wearing. If, on
the other hand, it's caused by risk compensation behaviour, then that's
caused (directly) by helmet wearing. If it's caused by increased
rotational injuries, that too is caused by helmet wearing. So whichever
of the hypotheses you believe (or if, like me, you believe it's a mix
of the three) then it's causal.

If, however, you believe that the increase in deaths with helmet wearing
is caused by little green men in spaceships with powerful rayguns then
I'd be prepared to accept that that was not causally related to
helmets. Unless, of course, the little green men had a phobia for
shiny-shelled beetles.

[1] You might claim that the decrease in cyclist numbers predated and/or
is independent of the introduction of helmets. Considering Britain in
isolation, that argument might hold water. But I don't think it holds
water when you compare Britain with otherwise similar states in Europe.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; may contain traces of nuts, bolts or washers.

Cliff said:

Well if you think that helmets don't reduce head injuries, then I suppose it
is best that you keep burying them in the sand.

There is no conclusive evidence that they make a net reduction in
/serious/ injuries. Have a look at the specifications they're built to,
and ask yourself if you really need protecting against such an accident
when they're unlikely to begin with.

If you think you /do/ need protection from this sort of risk then look
at the injury figures for falling down stairs or just slipping on foot
in the street, and tell me why you don't wear the same protection for
walking around.

Or perhaps you don't need any more head protection as your cranium has a
protective layer of sand all around it?

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Mark Thompson said:

Who benefits from seatbelt legislation not being disproved? Can't be
the evil multinational seatbelt conglomerates, surely? Maybe there
was worries over the drink drive testing - they thought that perhaps
it wouldn't have that big an impact and thought the seatbelt
legislation would bump the figures up a bit. Or, perhaps they were
designed to be mutually self supporting - they could point to the
drink drive legislation and point to a significant fall in KSIs, and
point to the seatbelt legislation and point to an (strangely enough)
equally high fall in KSIs.

If you've ever tried to make adjustments to a complex system of any
kind, from tuning an engine to tuning an operating system, you'll know
that it makes sense to change one thing at a time. That way you can see
what effect it's had and whether it makes things better or worse. If
you want to know what effect your changes have made it's generally a
bad idea change two variables at once. If you're a politician who wants
to be seen to be doing good works it might be better not to be able to
know what effect each change has as long as you can put a favourable
spin on the outcome.

If you commission a report to study the likely effectiveness of a
proposed measure, and the report tells you it will do more harm than
good, what do you do? If your concern is the general good you might
think it best to postpone the measure until you've had a chance to
study it further. If you're a politician who cares less about public
safety than his standing in the polls you might be tempted to suppress
the report, bring in the measure anyway, and muddy the waters by
simultaneously bringing in a second measure that is much more likely to
achieve the result you're looking for, even if it's somewhat diluted by
the first measure.

So, was it incompetence or cynical expediency? Hanlon's Razor suggests
the former but you'll have to decide for yourself.

--
Dave...