On Sat, 02 Jul 2005 14:24:39 +0100, Tilly <
[email protected]>
wrote:
>>The data from whole populations indicates that, if anything, the risk
>>of serious injury increases. You have to remember that the
>>probability of injury given crash is only half the story: the
>>probability of crash given ride also needs to be taken into account.
>OK. Lets look at the novice cyclist category. Where is there good
>evidence that helmets increase serious injury?
Reversed burden of proof. Where is the evidence they reduce the
incidence of serious injury, once crash frequency has been taken into
account?
>>Tilly, I asked for data showing that cycling is unusually dangerous.
>>Injury data form another country with no context (e.g. MV involvement,
>>comparable rates for pedestrians etc.) is not useful. Comparison of
>>child cyclists with all children in RTAs, failing to note the much
>>higher HI rate among child pedestrians, is not helpful.
>I haven't found any data that compares child cyclist head injury per
>distance or time with child pedestrian head injury per distance or
>time. If I did I would cite. Without that all I have is intuitive
>feeling, and my intuitive feeling it that for children time or
>distance on a bike runs a far far greater risk of head injury than
>time or distance on foot.
Right. But as has been shown many many times, intuitive feeling in
matters of risk management - not only helmets - is very often
completely wrong.
Which is why people like me tend to fall back on what data we do have,
which show the opposite of what you contend.
You want me to accept a position which is at odds with the data I
have, on the basis of your intuition. My intuition was completely
wrong on this, and I had to re-learn a lot of what I "knew" so you
will excuse me, I hope, if I prefer to ask for actual data.
>And I am disinclined to take either sides statements on trust, but am
>willing to interpret raw data from either side.
Then you have some reading to do
I have a library of several
hundred documents on this subject, and it is far from complete.
>In other words, if I read that 10 child (0-15) cyclists died as a
>result of head injury on Britain's roads I would trust that data. But
>if I read that 85% of head injury deaths would be prevented from
>helmet use I would not trust it.
Good. The former is available in Hansard, the latter comes as you
know from the 1989 Seattle study, the most widely-cited pro-helmet
paper in the world.
So, which raw data did you use to come to the judgment that helmets
reduce injury?
>>>That says nothing to convince me that telling a 4-9 year old novice
>>>cyclist to wear a helmet is wrong.
>>As I say, that is a reversal of the burden of proof. What evidence is
>>there to say it is right?
>Most children in the 4 - 9 age group do not have the cognitive skills
>to make a balanced decision.
No, no, you're begging the question again. We don't expect them to
make a rational decision on wearing a helmet while crossing the road,
because we don't think it's that dangerous. But the risk from
crossing the road is massively higher than that from riding (almost
all pedestrian injuries are sustained while crossing roads).
I am not questioning who makes the decision, I am questioning the
basis on which we assume a decision needs to be made in the first
place!
>>>For novice (4-9) cyclists:
>>>#1 They are unlikely to have the skills to take responsibility for
>>>cycle maintenance.
>>But we, as adults, do that for them.
>Yes. While training children it is the instructor's responsibility,
>but every lesson I take starts will a basic bike check, initially with
>me checking, then children checking each other's bikes, and at the end
>of the course them checking their own bikes: it's more difficult to
>check your own bike than someone else's.
My kids check their own and I double-check, but whatever.
>>>#2 This is what they are learning.
>>Neither of my children ever hit their head while learning to ride a
>>bike. Going down a slide, yes, but not riding a bike. Do you not
>>accept that the feeling of protection might encourage them to be less
>>careful? Might it interfere with the body's well-conditioned
>>protective reflexes?
>No. I understand what you say, but think that people rarely consider
>their helmet, consciously or sub consciously when riding, and that
>keeping safe is an overriding concern of cyclists.
So you say, but the limited published research on the issue disagrees.
There is a set of criteria for protective measures which will not
result in balancing behaviour, which helmets fail on two or three out
of four counts, and Mok et. al. demonstrated increased willingness to
take risks specifically in the case of children wearing cycle helmets.
You are forgetting, crashes are caused in the main not by the taking
of large risks, but by the taking of small risks very large numbers of
times.
Think of it like walking along a cliff. The closer you are to the
edge, the more likely you will fall off, even though the absolute
change in risk for each incremental move towards the edge is
imperceptible.
>>>#3 and #4 are irrelevant for playground cycling.
>>No, they are entirely relevant to cycling. You are not teaching them
>>so they can ride round the playground, you are teaching them so they
>>can have independent mobility, which is a precious thing denied to
>>many children in our increasingly hysterical society.
>They are relevant to cycling but not for novices. I would not
>consider speaking to a novice about road positioning when teaching
>them to cycle to Level 1A (get on and off the bike without help; start
>off and pedal without help; stop without help; ride along without help
>for at least one minute; make the bike go where they want), although I
>do at Level 1B (use their gears; stop quickly with control; manoeuvre
>safely to avoid objects; look all around, including behind, without
>wobbling; signal right and left without wobbling; carry out a simple
>bike check.)
My kids learned to ride bikes for transport.
>Light coloured clothing or hi-vis is of no benefit in the playground
>and do nothing to reduce risk.
There's not a lot of evidence it makes a difference on the road,
either...
>>>Which moves #5 to position #1 - unless I have missed something.
>>And no. 5 says: it may reduce the severity of some kinds of injury,
>>but won't make accidents less likely. Both of these are
>>question-begging to a degree. The first assumes that the injuries
>>prevented merit concern, the second that the feeling of protection
>>will not result in more risks being taken. I believe this is false,
>>and there is at least one paper which shows that helmeted children
>>will take more risks.
>I would say that children will only take more risks for a specific
>manoeuvre, not for general cycling.
But the only actual published peer-reviewed evidence of which I'm
aware says the opposite.
>>>I stand by my claim that it makes absolute sense for novice cyclists
>>>(4-9 years) to be compelled to wear helmets by those in loco parentis.
>>The word "absolute" is problematic. I can see no objective standard
>>by which that statement can be made or defended.
>I am quite happy to remove the word "absolute" from that statement.
I doff my cotton cycling cap to you, madam. Were you to say that in
your view it makes sense, then the statement would be (almost ;-)
uncontroversial.
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk
88% of helmet statistics are made up, 65% of them at CHS, Puget Sound
