From: JMS jmsmith2010 on
On Fri, 23 Apr 2010 13:25:35 +0100, Roland Perry <roland(a)perry.co.uk>
wrote:

<snip>

>>Perhaps you could quote a paragraph or two which mentions cyclists -
>>and the effect of risk compensation on them?
>>
>>I assume that cyclists are actually mentioned
>>
>>Are they?
>
>Cycle helmets pages 144-147
>
>But carry on being an ostrich, reading the book will be bad for your
>blood pressure.


You have the book - I haven't.

ffs - just post a paragraph : as per "Perhaps you could quote a
paragraph or two which mentions cyclists - and the effect of risk
compensation on them?"

Given that cycle helmets are mentioned - and there is an obvious
reluctance by you to repeat what is said - it is reasonable to
conclude that what *is* said does not support your argument.

ffs - just post a paragraph - not out of context - which shows that
there is a real effect of risk compensation regarding cycle helmets.
Why do you not just do that and put this disagreement to bed for once
and for all?





--

"wearing helmets can sometimes increase the chance of a cyclist being
involved in an accident."

That august body The CTC

(They've already had a slap for lying by the ASA)
From: Mike Clark on
In message <0aa3t51eq7o66thuttrivqv4sog5r6tr07(a)4ax.com>
JMS <jmsmith2010(a)live.co.uk > wrote:

> On Fri, 23 Apr 2010 13:25:35 +0100, Roland Perry <roland(a)perry.co.uk>
> wrote:
>
> <snip>
>
> >>Perhaps you could quote a paragraph or two which mentions cyclists -
> >>and the effect of risk compensation on them?
> >>
> >>I assume that cyclists are actually mentioned
> >>
> >>Are they?
> >
> >Cycle helmets pages 144-147
> >
> >But carry on being an ostrich, reading the book will be bad for your
> >blood pressure.
>
>
> You have the book - I haven't.
>
> ffs - just post a paragraph : as per "Perhaps you could quote a
> paragraph or two which mentions cyclists - and the effect of risk
> compensation on them?"
>
> Given that cycle helmets are mentioned - and there is an obvious
> reluctance by you to repeat what is said - it is reasonable to
> conclude that what *is* said does not support your argument.
>
> ffs - just post a paragraph - not out of context - which shows that
> there is a real effect of risk compensation regarding cycle helmets.
> Why do you not just do that and put this disagreement to bed for once
> and for all?
>
>

Are you prepared to regularly ride your bicycle without wearing a cycle
helmet? Do you know any other cyclists who insist on wearing a cycle
helmet when they ride a bicycle?

That's an example of risk compensation.

Mike
--
o/ \\ // |\ ,_ o Mike Clark
<\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing,
"> || _`\<,_ |__\ \> | caving, antibody engineer and
` || (_)/ (_) | \corn computer user"
From: Derek C on
On 21 Apr, 18:40, Peter Clinch <p.j.cli...(a)dundee.ac.uk> wrote:
> Derek C wrote:
> > So how do you explain the reduction in cyclist KSI figures, during a
> > period when cylehelmet wearing has become much more commonplace
> > without any compulsion? Seems like a far better correlation than
> > anything in cyclehelmets.org!
>
> I'll re-refer you to Hewson's 2005 piece in Tarfiic Injury
> Prevention: he covers the link (or lack thereof) rather more
> comprehensively (and is honest enough to draw attention to the
> weaknesses in the data).
>
> As Mike pointed out, correlation ain't necessarily causation, and
> with paragraphs like the one above you pretty much abdicate any
> benefit you may have had from a science education, at least as far
> as statistics are concerned.
>
> Pete.
> --
I think you are wriggling again Pete. I've had another read through
cyclehelmets.org and amongst other things it states that

'Cyclists who are more safety concious are more likely to wear cycle
helmets', so this explains any reduction in casualty rates for helmet
wearers. This rather contradicts the normal 'risk compensation'
argument I believe!

Real reductions in KSI rates are always attributed by cyclehelmets.org
to any other factors you can possible think of, other than wearing
cycle helmets. I will repeat that there has been a large increase in
the percentage of cyclists who wear helmets over the last 20 years or
so, and a large reduction in cyclist KSI. Due to the absense of a
parallel universe where nobody wears helmets to act as a control, I
can't categorically prove that helmets reduce serious head injuries,
but neither can you prove that they don't.

Derek C





From: Peter Clinch on
Derek C wrote:

> I think you are wriggling again Pete. I've had another read through
> cyclehelmets.org and amongst other things it states that
>
> 'Cyclists who are more safety concious are more likely to wear cycle
> helmets', so this explains any reduction in casualty rates for helmet
> wearers. This rather contradicts the normal 'risk compensation'
> argument I believe!

You're playing a great game of pick and choose. What is presented
falls into two broad categories: first, what /does/ happen, and
second, /possible/ explanation mechanisms.

The second are possibilities. They are not backed up with anything
like conclusive evidence, but are things that need further
consideration and investigation. They need that because the first
part is the important bit, and that is an actual track record of no
real effect in the Real World.

The exact mechanism of why they don't appear to do much good isn't
known. But it is an observable effect within the limitations of
the existing data that there's no effective reduction in KSI rates.
As (statistician) Nick Maclaren characterised it, zero effect
plus or minus error bars.

> Real reductions in KSI rates are always attributed by cyclehelmets.org
> to any other factors you can possible think of, other than wearing
> cycle helmets.

Because where you've had amazing rises in wearing rates there
haven't actually /been/ real reductions in KSI rates! Reductions
in KSIs are at the error bar level, not fundamental safety
improvement level.

> I will repeat that there has been a large increase in
> the percentage of cyclists who wear helmets over the last 20 years or
> so, and a large reduction in cyclist KSI. Due to the absense of a
> parallel universe where nobody wears helmets to act as a control, I
> can't categorically prove that helmets reduce serious head injuries,
> but neither can you prove that they don't.

You can't "categorically prove" anything either way with what we've
got, but yet again I re-refer you to Hewson's 2005 work in TIP as a
pretty fair start in that direction. Why not go and read it rather
than pre-judge the content?

You just wave your arms and say "you can't prove that so my gut
reaction is better!" rather than actually do the real reading. If
you're going to do that it's your perogative but you really
shouldn't go around pretending it's anything like science.

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 p.j.clinch(a)dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/
From: Roland Perry on
In message <0aa3t51eq7o66thuttrivqv4sog5r6tr07(a)4ax.com>, at 15:10:33 on
Fri, 23 Apr 2010, JMS <jmsmith2010(a)live.co.uk> remarked:
>On Fri, 23 Apr 2010 13:25:35 +0100, Roland Perry <roland(a)perry.co.uk>
>wrote:
>
><snip>
>
>>>Perhaps you could quote a paragraph or two which mentions cyclists -
>>>and the effect of risk compensation on them?
>>>
>>>I assume that cyclists are actually mentioned
>>>
>>>Are they?
>>
>>Cycle helmets pages 144-147
>>
>>But carry on being an ostrich, reading the book will be bad for your
>>blood pressure.
>
>You have the book - I haven't.

That line of argument is a slippery slope. It leaves you open to being
asked to quote your sources.

>ffs - just post a paragraph : as per "Perhaps you could quote a
>paragraph or two which mentions cyclists - and the effect of risk
>compensation on them?"
>
>Given that cycle helmets are mentioned - and there is an obvious
>reluctance by you to repeat what is said - it is reasonable to
>conclude that what *is* said does not support your argument.

He quotes Mayer Hillman, for example, saying "in the first major study
of cycle helmets" he had "surveyed the growing body of evidence from
other risk taking, that shows that the use of protective equipment and
safety devices modifies behaviour".

>ffs - just post a paragraph - not out of context - which shows that
>there is a real effect of risk compensation regarding cycle helmets.
>Why do you not just do that and put this disagreement to bed for once
>and for all?

OK, done what you asked.
--
Roland Perry