From: Peter Clinch on
Derek C wrote:
>
> Oh dear, the 'confounding factors' argument again!

You missed the confounding factors of plenty of places experiencing
no safety benefit from seat belts, and actually greater cyclist/ped
casualties. Not in the UK, but other legislation such as harsher
drink/drive regime /could/ account for that.

> If the risk
> compensation theory was true (as cars get safer, motorists take bigger
> risks), we would still be getting 8000 road deaths per annum in the
> UK, rather than less than 3000.

RC doesn't state that there will be just as many accidents for all
things all the time. If you're suggesting it does then you're
being naive and simplistic.

> As to the one exception disproves the rule theory, where you quoted
> one elderly cyclist who died despite wearing a helmet, and another one
> who survived despite not wearing one. This is just an example of
> random chance as applied to individual accidents.

You've got the wrong end of the stick /again/. It /is/ just an
example of random chance, but what you missed is that you don't
actually know your example wasn't.

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: Derek C on
On 22 May, 10:14, Peter Clinch <p.j.cli...(a)dundee.ac.uk> wrote:
> Derek C wrote:
>
> > Oh dear, the 'confounding factors' argument again!
>
> You missed the confounding factors of plenty of places experiencing
> no safety benefit from seat belts, and actually greater cyclist/ped
> casualties.  Not in the UK, but other legislation such as harsher
> drink/drive regime /could/ account for that.

I understand that the UK blood alcohol limit for driving is relatively
high compared with many other comparable countries. We have a limit of
80mg/100ml BAC compared with 50mg/100ml or even zero in other EC
countries.
>
> > If the risk
> > compensation theory was true (as cars get safer, motorists take bigger
> > risks), we would still be getting 8000 road deaths per annum in the
> > UK, rather than less than 3000.
>
> RC doesn't state that there will be just as many accidents for all
> things  all the time.  If you're suggesting it does then you're
> being naive and simplistic.

Seems like a fairly convincing and statistically significant reduction
in road deaths to me.
>
> > As to the one exception disproves the rule theory, where you quoted
> > one elderly cyclist who died despite wearing a helmet, and another one
> > who survived despite not wearing one. This is just an example of
> > random chance as applied to individual accidents.
>
> You've got the wrong end of the stick /again/.  It /is/ just an
> example of random chance, but what you missed is that you don't
> actually know your example wasn't.
>
I accept and agree with that, but as the lad landed very heavily on
the front and top of his head, judging by the damage to the helmet and
his face, there is a good probability that the helmet did prevent more
serious injury. I assume that a senior hospital A&E consultant has
seen plenty of similar cases, so is able to make a judgement based on
his own experience. How do you know that your example was?

Derek C
From: Tony Raven on
Adrian wrote:
> Derek C <del.copeland(a)tiscali.co.uk> gurgled happily, sounding much like
> they were saying:
>
>> I understand that the UK blood alcohol limit for driving is relatively
>> high compared with many other comparable countries. We have a limit of
>> 80mg/100ml BAC compared with 50mg/100ml or even zero in other EC
>> countries.
>
> I've yet to see any figures to suggest how many KSIs are due to people
> driving with BAC between 50 & 80.
>

There is good evidence from the US that the reduction from 100 to 80 led
to a significant reduction in deaths [1] and a study of blood alcohol
levels of drivers in hospital found that 13% of those who tested
positive were below 80 [2]

[1] Shults RA, Elder RW, Sleet DA, et al. Reviews of evidence regarding
interventions to reduce alcohol-impaired driving. American Journal of
Preventive Medicine 2001;21(4S):66–88.
[2] Walsh JM et al, Drug and alcohol use among drivers admitted to a
Level-1 trauma center, Accident Analysis & Prevention 37(5) September
2005, Pages 894-901

Recent drugs use also featured significantly (51% tested positive) with
marijuana and cocaine being the most prevalent followed by amphetamines.
At present there is no drugged driving law or testing.


--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell
From: Tony Raven on
Sniper wrote:

>
> Going back to my law degree I leave you to your musings...
>
> Sniper:
>

Good grief, a police officer studying the law? Whatever next?

--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell
From: Derek C on
On 22 May, 12:06, Sniper <Sniper8...(a)yahoo.co.uk> wrote:
> The best that can be said of cycle helmets is they may save some minor
> injury...
>
> The worst that can be said of cycle helmets is that they may cause some
> avoidable fatalities...
>
> The assertion that a cycle helmet may or will save your life is
> undoubtedly a fallacy based in poor understanding of basic principles of
> physics and engineering.
>
> A cycle helmet, when smashed to bits, is frequently described as 'having
> absorbed the impact' or having 'done its job' Whereas in truth it has
> simply failed... it failed to absorb any impact as the load applied
> exceeded its capability to transfer that load across its surface hence
> it failed.
>
> A motorcycle helmet exhibiting a similar result would not be passed as
> fit for sale... in a collision, even with a head on impact a motorcycle
> helmet is expected not to fail e.g. be reduced to a broken shell.
>
> Ergo: a cycle helmet in pieces has failed...
>
> Ergo: a cycle helmet that will not transfer loads without failure above
> the fracture frequency load currently in use is unlikely to save one's
> life in a cycle/motor vehicle collision: it may dissipate a bump to the
> head and save minor injury in a 'non direct impact' fall, e.g. where
> impact of the head is secondary: but, where the forces involved are
> sufficient to cause death in a non helmet wearing cyclist then the
> wearing of a cycle helmet will not alter that outcome until cycle
> helmets are sufficiently strong enough to withstand the forces applied
> to them during 'direct impact - fatal load' collisions... at which point
> a new series of fatality questions might possibly be presented.
>
> Going back to my law degree I leave you to your musings...
>
> Sniper:

The helmet in the example given had not split or failed in any way. It
was slightly dented at the front and some bits of foam had been gouged
out to the depth of a few millmetres, presumable as a result of
hitting a paved or tarmaced surface. Cycle helmets are essentially one
shot devices that should be thrown away after any significant impacts.
Actually they are two shot to absorb initial and secondary impacts.

Motor cycle helmets would be much too heavy and poorly ventilated for
cycling use, and also impair your hearing which is a good defence
mechanism for cyclists who can hear vehicles coming (except for
electric hybrids). Heavy helmets increase the risk of a neck injury in
high g decelerations, which is why racing drivers wear those helmet
restraint devices on their shoulders.

Derek C