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#521
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Invisible Cyclists in Solstice Dark
In uk.rec.cycling SMS twisted the electrons to say:
Hmm, I see that you claimed this in a letter, but I never saw them make that claim. He claimed it in a letter using the figures that they provided in their report. If you beleive him to be in error, then should you should show how and why. You're never going to get full marks in the exam if you don't show your working out! grins -- These opinions might not even be mine ... Let alone connected with my employer ... |
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#522
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Invisible Cyclists in Solstice Dark
On Fri, 06 Jan 2006 14:35:59 -0800, SMS
said in : This one, where Cook and Sheihk (authors of the book "Basic skills in statistics") claimed that helmets prevented 186% of accidents: Hmm, I see that you claimed this in a letter, but I never saw them make that claim. It's very simple, just do the maths correcting their schoolboy error. Guy -- http://www.chapmancentral.co.uk "To every complex problem there is a solution which is simple, neat and wrong" - HL Mencken |
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Invisible Cyclists in Solstice Dark
On Thu, 05 Jan 2006 23:37:08 GMT, Mike Rice said in
: Yes, Steve reckons that the tiny side-facing LEDs in the TL-1000 will provide a level of protection against side impacts massively greater than that which the (far brighter) rear-facing LEDs in cheaper rear lights afford against rear impact. I think in ScharfWorld rear impacts are more common than they are on planet earth :-) Guy I generally agree with you, but I use a TL 1000 and really like it. One problem I had with my older LED rear light was that occassionally the battery would jostle loose and the light would stop functining. Because it was rear firing I would not be aware that it was out until arriving at my destination and dismounting. I have an LD1000 on the Brom. But the LEDs are no more visible from the sides than the main LEDs on my several B&M 4D TopLites. More importantly, we both know that the side LEDs are not large. Scharf, in a previous post, was denouncing competing LED lights as being insufficiently bright, but suggesting that the side LEDs in the TL-1000 could prevent side impacts - a logically inconsistent position, as I'm sure you'll agree. My biggest problem with Scharf on the issue of lights is this: he asserts that *only* very bright lights are adequate. Since I know of no evidence that lights make any difference at all, however much I spend on them (which is a lot), I don't think Scharf's assertion holds water. I am not alone in this :-) Of course I think the best method of preventing side impact crashes is to ride defensively and never trust a driver with your safety. Quite. Guy -- http://www.chapmancentral.co.uk "To every complex problem there is a solution which is simple, neat and wrong" - HL Mencken |
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Invisible Cyclists in Solstice Dark
SMS wrote:
James Annan wrote: SMS wrote: Alan Braggins wrote: Ah, but we know that in some studies, helmets protect against more than 100% of injuries. Huh? Which studies were those? This one, where Cook and Sheihk (authors of the book "Basic skills in statistics") claimed that helmets prevented 186% of accidents: Hmm, I see that you claimed this in a letter, but I never saw them make that claim. It's the bit where they write: "Assuming that the difference between cyclists and pedestrians (3.6%) is attributable to helmet wearing, and with helmet wearing having increased by 5.8%, we estimate that helmets prevent [erroneous calculation] of serious head injuries." http://ip.bmjjournals.com/cgi/content/full/9/3/266 Using their assumptions, the correct calculation gives 186%. They didn't quote that number because they got their sums wrong - a point which they did explicitly acknowledge in their reply to my letter. Their data actually prove clearly that there are large uncontrolled factors other than helmet-wearing which dominate the observed changes in head injury rate. The authors make no attempt to investigate or quantify any of these effects. They assumed a priori that helmets would be the biggest effect, and because they got their sums wrong, they never realised that the data contradict this belief. James -- James Annan see web pages for email http://www.ne.jp/asahi/julesandjames/home/ http://julesandjames.blogspot.com/ |
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Invisible Cyclists in Solstice Dark
Just zis Guy, you know? wrote:
Which is, presumably, why you keep banging on about it, since the measures for which we have a reasonable estimate of exposure all show that cycling is actually quite safe, 'Actually quite safe.' You mean 30 times more likely to cause injury per mile than driving actually quite safe (Moritz)? and we all know how that idea offends your macho bike messenger pride :-) Indeed, my macho bike messenger pride is offended. Robert |
#526
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Invisible Cyclists in Solstice Dark
wrote:
The following is not a scientific paper, but it does refer to the rise in head injury rates in the US, despite the growing popularity of helmets. http://www.magma.ca/~ocbc/nytimes.html - Frank Krygowski The main points in this New York Times 2001 article http://www.magma.ca/~ocbc/nytimes.html (cited by Frank Krygowski) - I've summarised here.. http://www.beseenonabike.com/bsoab/b...facts.htm#head - the rate of head injuries per active cyclist has increased 51 percent just as bicycle helmets have become widespread. Why? Reasons cited in the above article, for this increase in head injuries with increased helmet use a- - Helmets are worn incorrectly, for example, helmet worn to far back leaving forehead unprotected - Daredevel Effect: with a helmet, cyclists may feel an inflated sense of security, may ride faster and take more risks. A parallel situation is anti-lock brakes, when introduced ABS brakes were supposed to reduce accidents, but drivers realized their brakes were more effective & they started driving faster - (some) accident rates rose. - to reduce the Daredevil Effect "you would be well advised to wear a helmet provided you could persuade yourself it is of little use" And - "patients who were wearing helmets when they were injured are much better off than those who were not" - "Bicycle helmets are the best technology we have for protecting the brain, the helmets serve the function of an air bag." Chris Street www.BeSeenOnABike.com |
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Invisible Cyclists in Solstice Dark
gds wrote:
Clive George wrote: Um - no? If the total number of injuries severe enough to require hospital treatment remains the same regardless of the fact that more helmets are being worn, that indicates to me that wearing a helmet doesn't affect my chance of getting seriously hurt in x years/km of cycling - the measure I mentioned above as being the important one. The problem with the hypothesis you present above - that helmets make some accidents minor and hence unreported - is that there doesn't appear to be a corresponding reduction in the serious injuries suffered. If the number of accidents remained the same, the helmets aren't working. If the helmets are working, the number of accidents has gone up. Either way the chance of getting a serious injury - which is as I may have said before, the only important factor here - is not reduced. Not quite! Despite prsentations on the effect of mandatory helmet laws and decreased ridership in some areas there is also separate data showing that, for example, in the US bicycle ridership has increased during the same time that helmet sales and use increased (no mandatory effect). Call it the Lance effect or whatever ( a few years ago it was the Greg Lemond effect). So, we also need to understand the denominator. If bicycle miles and/or time increased during the period in which helmet use increased you could have the result that the same number of serious accidents represented a smaller accident rate and you could hypothesize that the rate reduction was due to helmet use. Again, I'm not arguing that that is so; merely that without understanding all of these variables you can't possible understand the totality of what is happening. Yes you are arguing that it is so when it isn't. The denominator is understood. It is measured by a number of different methods, none of them perfect. But if you make a measurement ten different ways and they all come out with roughly the same number you have a reasonable level of confidence that it right and certainly it is more likely to be right than wrong. In which case the conclusions on pre mile risk that helmets do not help is more likely to be right than wrong - something you seem to be desperate to deny It seems to me that lots of you folks seem to oppose helmets stemming out the mandatory situation in some jurisdictions. I can sympathize with that sentiment. But I don't think the way to address it is to pretend you have good statistical evidence when you don't. I'm all for letting folks decide for themselves-- and Ijst wish everyone had much better data on which to base that decision. The data is of varying quality - there are some very competent studies and some crap ones like TR&T. However the credible statistical evidence is overwhelmingly in support of helmets at best not helping and possibly making the situation worse. By credible I rule out studies that show that helmets prevent 75% of leg injuries or 186% of head injuries. The most statistically robust studies are the time series studies where a step change in helmet use took place due to MHLs and confounding factors can be largely ruled out. When all the different studies in different countries by different methods tell you one thing the probability is that that thing is more likely to be right than wrong. Something again you seem desperate to deny. -- Tony "The best way I know of to win an argument is to start by being in the right." - Lord Hailsham |
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Invisible Cyclists in Solstice Dark
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#529
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Invisible Cyclists in Solstice Dark
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