helmets increase danger
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From: Peter Clinch on 19 Apr 2010 06:39 Derek C wrote: > I'm glad to hear that there are some sensible members of the CTC! Tim Gill is one. He wears a helmet too, but in his summary of cycling safety for children and young people he presents a very well done precis of the helmet debate, in which he concludes there's much less of a clear conclusion than you seem to think there is. He at least has the grace to admit that his wearing is based on a "what if" gut feeling rather than rigorous science. http://www.ncb.org.uk/dotpdf/open%20access%20-%20phase%201%20only/cyclingreport_timgill_200512.pdf is worth your while reading. Back to the question from before though: in whose vested interest is it to deprecate the perceptions of cycle helmet efficacy if they really are a particularly worthwhile safety measure? 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: Albert T Cone on 19 Apr 2010 06:44 JMS wrote: > On Fri, 16 Apr 2010 15:59:35 +0100, Albert T Cone > <a.k.kirby(a)durham.ac.uk> wrote: > >> JMS wrote: >>> On Tue, 06 Apr 2010 17:13:39 +0100, Albert T Cone >>> <a.k.kirby(a)durham.ac.uk> wrote: >>> >>>> JMS wrote: >>>>> Are you against them by any chance? >>>> No. I don't wear one myself, if you are interested, because I prefer >>>> the risk of abrasions and blunt trauma injury to those of torsional >>>> injury to the neck and spine. Other people may weigh those risks >>>> differently, but I think that it *should* be a personal choice, and I am >>>> not in favour of making helmet wearing mandatory. >>> >>> I was not aware that there was any discussion about making helmets >>> mandatory in the thread. >>> >>> I do however love the way that those who are actually anti-helmet like >>> to introduce the "compulsory argument" when all else fails. >>> >>> Well done. >> I'm afraid that's a straw man. I am not anti-helmet, I simply think, >> based on the evidence as I understand it, that *for me* the balance of >> risk/severity of injury is better if *I* don't wear a helmet. >> >> I do think that the general perception of the efficacy of helmets is not >> supported by the evidence. I would prefer that people were better informed. >> >> It is a single logical step from me making an informed personal choice >> to others doing the same, and then one more to the issue of compulsion, >> so it is unfair to suggest that this was a last-ditch attempt to divert >> attention from a supposedly failing argument. >> >> >>> And the chance of "torsional injury to the neck and spine." through >>> wearing a helmet is what exactly? >> If you mean to query the mechanism, then it is is described well in: >> J.H. Adams, D.I. Graham, L.S. Murray and G. Scott , Diffuse axonal >> injury due to non-missile head injury in humans. Ann. Neurol. 12 (1982), >> pp. 557�563 >> >> Evidence that cycling helmets do in-fact contribute to axial torque is >> given in: >> Andersson, T., Larsson, P., Sandberg, U., 1993. Chin strap forces in >> bicycle helmets, Swedish National Testing and Research Institute, >> Materials and Mechanics, SP report 42 >> >> If you mean for me to quantify the risk, then I can't - the statistics >> are unclear, for all aspects of helmet safety. The potential severity >> of the injury, *in my opinion*, is such that I give it higher weighting >> than the potential for abrasion and concussion. Others' opinion may vary. > > > I have looked at the papers - thanks for the links > > I understand that you are unwilling/unable to answer the question : > > "And the chance of "torsional injury to the neck and spine." through > wearing a helmet is what exactly?" > > In which case - perhaps you could point out a paragraph which > actually says that wearing a cycle helmet will (or perhaps even "may") > increase the torsional injury to the neck and spine by any measure at > all as I cannot see such. In: "The efficacy of bicycle helmets against brain injury.", Curnow WJ., Accident Analysis and Prevention, 2003,35: pp287-292 you will find: "Ommaya et al. (1971) reported that such experimental work supported Holbourn�s view that only skull damage and rotation of the head are important and that pure (linear) head translation had never been demonstrated as an injury producing factor for the brain.... Graham et al. (1995) noted that DAI is the commonest cause of disability after head injury, including the vegetative state... Tests of impacts on asphalt at 34km/h have since shown that soft helmets grab the surface, rotating the head and pro- ducing high angular accelerations (Andersson et al., 1993). Ventilation holes might well aggravate this effect." I can't see any difficulty in understanding the mechanism; any force applied at a distance from a centre of rotation, results in a torque. The magnitude of the torque is the (vector) product of the force and the off-axis distance. In other words, if you rub your head along a frictional surface, there will tend to be a twisting action on it. if you make your head bigger, that torque is larger. Given that the mechanism is deterministic, the question becomes one of probability - how significant a contribution does this effect make? As I have said, the statistics are rather unclear, but studies, both on primates and simulated, as well as several of the statisistical analyses strongly suggest that it is not only a real and observed effect, but a rather common one.
From: Peter Clinch on 20 Apr 2010 04:20 Derek C wrote: > On 19 Apr, 19:54, Peter Clinch <p.j.cli...(a)dundee.ac.uk> wrote: >> Derek C wrote: >>> So why are there about 2500 reported killed and seriously injured >>> cyclists in the UK every year? Only about 2% of journeys are made by >>> bicycle, but cyclists make up 9% of the total KSI (killed and >>> seriously injured) in UK road accidents. This figure has fallen from >>> about 6500 in the mid1980s, a period during which helmet wearing has >>> become much more commonplace! Figures from the DfT. >> Let's be clear... You /are/ the same person criticising BHRF for >> hilariously inept use of statistics, yes? > So are you claiming that the DfT (not my) statistics are incorrect > then? Certainly not. But nor am I implying, as you quite clearly do with your exclamation marked aside, that helmet use is a factor. See Hewson's 2005 work in TIP for a much more detailed analysis of the degree to which helmet wearing has or hasn't affected the trends for KSIs amongst cyclists. I didn't say your figures were inaccurate, simply that the use to which you put them remains ridiculous. And I think that if you saw that sort of daft, unsubstantiated implication in a helmet-ecpetic paper you would (quite rightly) haul it over the coals. But if you're going to make anything of your scientific training you need to haul your /own/ conclusions over the coals if they're not remotely rigorous, and that's something you've consistently failed to do. In other words, you've always appeared to have a much higher tolerance for rubbish if it happens to fit your predetermined conclusion, which is shockingly poor 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: Mike Clark on 20 Apr 2010 07:37 In message <57lps5p96hpjn6airnpr0e3ctcrf543ct1(a)4ax.com> JMS <jmsmith2010(a)live.co.uk > wrote: > On Mon, 19 Apr 2010 19:25:44 +0100, Mike Clark <mrc7--ct(a)cam.ac.uk> > wrote: > > >In message <be3a3aaa-61f3-4bb3-8f4a-3bef92de6773(a)b33g2000yqc.googlegroups.com> > > Derek C <del.copeland(a)tiscali.co.uk> wrote: > > > >> On 19 Apr, 16:47, Mike Clark <mrc7-...(a)cam.ac.uk> wrote: > >[snip] > >> > What is an "average cyclist"? As far as I can see from looking at > >> > the statistics the "average cyclist", is a cyclist who never has a > >> > serious injury as a result of a cycling accident. > >> > > >> > >> So why are there about 2500 reported killed and seriously injured > >> cyclists in the UK every year? Only about 2% of journeys are made by > >> bicycle, but cyclists make up 9% of the total KSI (killed and > >> seriously injured) in UK road accidents. This figure has fallen from > >> about 6500 in the mid1980s, a period during which helmet wearing has > >> become much more commonplace! Figures from the DfT. > >> > >> Derek C > > > >You've given me the numbers for cyclists who have been reported as > >having had a serious accident. You've conveniently ignored the total > >number of cyclists, or number of cyclists who haven't been reported as > >KSI'd. > > > >I was addressing the discussion about averages, not extremes of the > >distribution. > > > >What is your definition of an "average cyclist"? > > If it really worries you - why not ask the DTi - it is a term which > they use often in their reports. > > How about - it's not the man on the Clapham Omnibus - it's the woman > who rides up its inside :-) > Ah I see you are going for a colloquial usage of "average cyclist" as opposed to a statistical one? Presumably that's why you don't think that the average cyclist has (slightly) less than two eye's, two arms and two legs? I'm more inclined to the view that the more appropriate average to consider in this case is the mode, or perhaps the median, rather than the mean. However whichever of the three values that you choose to accept as the average, you'll come to the conclusion that the average cyclist does not encounter a fatal accident or serious injury whilst cycling. Mike -- o/ \\ // |\ ,_ o Mike Clark <\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing, "> || _`\<,_ |__\ \> | caving, antibody engineer and ` || (_)/ (_) | \corn computer user"
From: Mike Clark on 19 Apr 2010 11:47
In message <gbsjs5p9lja7v22l6p489n68qequrnhddg(a)4ax.com> JMS <jmsmith2010(a)live.co.uk > wrote: [snip] > > That does not make the question I posed invalid. > What is an "average cyclist"? As far as I can see from looking at the statistics the "average cyclist", is a cyclist who never has a serious injury as a result of a cycling accident. Mike -- o/ \\ // |\ ,_ o Mike Clark <\__,\\ // __o | \ / /\, "A mountain climbing, cycling, skiing, "> || _`\<,_ |__\ \> | caving, antibody engineer and ` || (_)/ (_) | \corn computer user" |