Bob Mannix wrote:
> First, you didn't hear the crack!
No, but I have looked at the EN1078 helmet specification and I have seen
the population figures that show /no/ discernible effect on serious and
fatal head injuries by marked increase of helmet wearing.
The crack was (I'm obviously guessing here) brittle failure in the
helmet, in which mode a helmet absorbs remarkably little energy. In
order to work as advertised they must deform, and that doesn't make a
cracking noise. Skulls tend not to undergo brittle failure at these
sorts of energies. Now, I'm not saying he wouldn't have had any reason
to be glad of the lid, but I am simply coming out of a single anecdote
and looking at the whole population figures which show /no/ improvement
in serious/fatal head injuries for increased helmet use.
> the only such accident I have witnessed but one would have been enough for
> him, I suspect. Cycling home from work (as it was) car drivers are tired and
> preoccupied with work things and are more likely to run into you.
Look at EN1078: it is /not/ designed to protect you in collision with
other vehicles, all it's up for is basically a fall from a stationary
cycle. Get much past these energies and you get things like brittle
failure, which absorbs very little energy...
> For that
> reason, I wear one if cycling to work (no it is a rare event, I'm afraid)
> but don't into town on a Saturday. Compulsion would be silly though.
I have no objection to people wearing them, but I do want them to
realise that they have no record that is visible in population data of
improving safety in terms of serious injuries in vehicle collisions. If
you want to save the possibility of a bump and graze they should do
that, and that's why I wear mine on the MTB where I'm doing relatively
daft stuff and there's a good chance of parting company with the bike.
> The simple fact is wearing one has to be beneficial in safety terms
That's what I thought for years, and always wore one. Being pointed at
the literature started doubts, and they've got bigger the more I read.
u.r.cycling has quite a few people like that, including several
professional scientists who are /good/ at reviewing literature and
poking holes where they exist.
I repeat, there is /no/ conclusive evidence that they will save you a
serious head injury.
> I think it was in this neg someone said life was about minimizing
risk. I
> posted a disagreement in the sense that I said life is about managing risk,
> not minimizing it.
Yes, but a cycle helmet is minimising risk of a bump and graze, it
doesn't demonstrably do anything to your risk of serious injury. Look
at the data.
> As you kind of suggest (albeit at the cost of bring domestic stairs into the
> conversation!) few of us know people who have had serious injuries as a
> result of not wearing a cycle helmet, when apparently hundreds have cycled
> into the back of parked cars and knocked bits off their front teeth! -
> perhaps gumshields should be compulsory? We all know someone who has been
> killed in a car or motorbike accident.
One must be wary of anecdotal evidence. It's quite persuasive to most
people, but it's no substitute for large datasets and/or experiments
with reliable controls. "A helmet saved my life" is quite common in
cycling circles, but as discussed at cyclehelmets.org, that doesn't
really mean much except a degree of misunderstanding about how much
their life was in danger. I had such an anecdote myself, until I found
out about the brittle failure problem, in fact, so I've Been There and
Done That in the "they must do some good!" stakes.
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 protected] http://www.dundee.ac.uk/~pjclinch/
