From: Peter Clinch on
Derek C wrote:

> So you have a 75% chance of being buried in an avalanche without being
> killed by the initial trauma then. Sounds like good odds to me, if the
> safety equipment allows you to be dug out alive!

But a great many of those 75% die from asphyxiation before being
rescued. The odds are never good in avalanches, as with bike crashes
the best defence, by several orders of magnitude, is don't be in one.
The primary use of a shovel in avalanche safety isn't digging out
victims but digging snow-pack assessment pits to give an estimate of how
safe a slope is. A rescue beacon is a last resort and goes with crossed
fingers when everything's already gone The Way Of The Pear.

In other news, any chance of that quote from the CTC saying not to use
helmets?

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: Mike Clark on
In message <0d427ed8-ec1d-4655-ade0-fc063f5a6380(a)12g2000yqi.googlegroups.com>
Derek C <del.copeland(a)tiscali.co.uk> wrote:

> On 26 Apr, 10:34, Mike Clark <mrc7-...(a)cam.ac.uk> wrote:
> > In message <o974t5l2m6scmijaelb830u281aa9et...(a)4ax.com>
> > � � � � � JMS <jmsmith2...(a)live.co.uk > wrote:
> >
> >
> >
> >
> >
> > > On Fri, 23 Apr 2010 15:23:09 +0100, Mike Clark <mrc7-...(a)cam.ac.uk>
> > > wrote:
> >
> > > <snip>
> >
> > > >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
> >
> > > Yes - many thanks for a tremendous contribution.
> >
> > > I c an see that you are an expert on the subject.
> >
> > That some individuals change their behaviour in response to
> > perceived risk is self evident. What is more problematic is
> > calculating the impact of those individual responses at a population
> > level.
> >
> > At a gross level, willingness to indulge in an activity only if
> > using particular safety equipment (even where that safety equipment
> > does not provide full protection) is an obvious form of risk
> > compensation.
> >
> > For example I do not go ski-mountaineering without wearing an
> > avalanche transceiver and carrying a shovel and probe. Do these
> > items of equipment prevent me from being avalanched? No they don't.
> > Do they offer some degree of hope rescue if I am? Yes they do.
> > However if I didn't go off-piste my chances of being avalanched are
> > very low. If I do they are much higher. But since about 25% of
> > avalanche victims are killed by the trauma of the avalanche, then
> > all the transceiver will be good for is assistance in finding my
> > body. So I know that I'm prepared to take a greater risk of exposure
> > to danger that is only partly mitigated by the safety equipment I
> > use.
>
> So you have a 75% chance of being buried in an avalanche without being
> killed by the initial trauma then. Sounds like good odds to me, if the
> safety equipment allows you to be dug out alive!
>
>
> Derek C

The problem is "IF the safety equipment allows you to be dug out alive"

25% is the approximate proportion killed in the initial trauma, eg being
crushed, pushed over a cliff, neck broken etc.

IF you survive the initial avalanche then your chance of rescue alive
decreases from about 90% if dug out within 15 minutes, to only 30% after
35 minutes (due to suffocation).

In France which is well equipped to deal with avalanches in can take the
best part of an hour for helicopter transported professional rescuers to
arrive so they usually end up recovering bodies. Your best chance of
survival is if your companions are not caught by the avalanche and they
have sufficient skills to locate you within 10-15 minutes.

I've practised this a lot and it isn't at all easy to reliably get down
to that time, and that's under a controlled situation not a real crisis.

So in this example the availability and use of the safety equipment is
likely to be a factor that encourages more people to be prepared to take
the risks off-piste, yet in doing so they are definitely increasing
their risks of serious injury and death. Thus over time the improvements
in safety equipment may lead to more victims.

We as individuals often tend to exhibit similar behaviour in taking
risks in many activities that we do including driving and cycling. If
you buy a car with better brakes and better handling, you may have a
tendency to drive faster, brake later and corner faster. As an opposite,
if you are given a car which you are unfamiliar with, or which seems to
show poor handling, you're more likely to drive it cautiously.


Mike
--
o/ \\ // |\ ,_ o Mike Clark
<\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing,
"> || _`\<,_ |__\ \> | caving, antibody engineer and
` || (_)/ (_) | \corn computer user" http://www.antibody.me.uk/
From: Tony Raven on
Mike Clark wrote:
>
> So in this example the availability and use of the safety equipment is
> likely to be a factor that encourages more people to be prepared to take
> the risks off-piste, yet in doing so they are definitely increasing
> their risks of serious injury and death. Thus over time the improvements
> in safety equipment may lead to more victims.
>

There is a classic example of this in Sunshine/Banff where to ski an
area called Delirium you have to pass through a gate where they check
you have a transceiver and shovel and that you are skiing with a
partner. So everyone rents the gear in town. There is zero check on
whether you have a clue how to use it. In fact the restrictions add to
the Delirium reputation and attract more people to try it so they can
say they skied it as you can tell immediately by listening to
conversations in the bars and on the slopes.


--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell
From: ke10 on
In article <YhUXDBm4pc1LFAvN(a)perry.co.uk>,
Roland Perry <roland(a)perry.co.uk> wrote:
>In message <hr3qo8$795$1(a)soup.linux.pwf.cam.ac.uk>, at 11:43:20 on Mon,
>26 Apr 2010, ke10(a)cam.ac.uk remarked:
>>In article <Dfjx80ej$c0LFAmB(a)perry.co.uk>,
>>Roland Perry <roland(a)perry.co.uk> wrote:
>>>
>>>That would not have been true. I did the first year Statistics course in
>>>the Maths Faculty, as a 1/3 of my third-year course in the Engineering
>>>department.
>>
>>Remarkable. At present there is no stats course in the first year in
>>the Maths Faculty, though there is a probability course,
>
>I did my course 40 years ago (oh dear, that makes me feel old). They
>were very much into "game theory" if that helps you understand which
>module it was. Maybe Dr Conway (he who sings a little flat) would
>remember it (is he still alive?)

Well, it's not worth a great deal of argument, but if there was a first-year
course called statistics (which there may well have been), it was not more than
an eighth of the first-year Tripos. Your dates fall into the six years
between the time I was here as an undergraduate and the time I started teaching
here, but the Tripos didn't change much in that period.

Out of idle curiosity, I have looked up the 1968 first-year Tripos papers.
Stats and probability accounted for four questions out of ten on one of the
five papers, which means it was at most a 24-lecture course, more likely 16.
So I still think turning it into one-third of a third-year course
is a neat trick.

As far as I know John Conway is alive and working at Princeton.

Katy
From: Roland Perry on
In message <hr6qnd$mmn$1(a)smaug.linux.pwf.cam.ac.uk>, at 15:01:17 on Tue,
27 Apr 2010, ke10(a)cam.ac.uk remarked:

>Out of idle curiosity, I have looked up the 1968 first-year Tripos papers.
>Stats and probability accounted for four questions out of ten on one of the
>five papers, which means it was at most a 24-lecture course, more likely 16.
>So I still think turning it into one-third of a third-year course
>is a neat trick.

I seem to remember trooping down to the New Museums site much more often
than that. Maybe it was some other course, no idea what though. Mine was
Engineering Part "F", 1973-4, if that helps.
--
Roland Perry