There are some invalid assumptions that are almost always made in discussions of this subject that are worth pointing out. Regarding risk compensation, for example, it's not just the cyclist who may change behavior when wearing a helmet; others who see him may also behave differently (I'm thinking of the overtaking study done by Ian Walker). The same could easily be true for automobiles (do other drivers take more care around Smart cars than large SUVs?). Also, more particular to helmets, it is usually assumed that the helmet has no effect on either the probability of an impact to the cyclist's head or the nature of that impact, but this is a false assumption, as a helmet increases the effective size and mass of the wearer's head. A near miss without a helmet could turn into a severe neck injury, for example.
Another type of assumption that comes up consistently is one of causality. In many cases, the data show an association between helmet use and a decreased incidence of head injuries, and it is usually assumed that the helmet use was the cause of that decrease, but this is a fallacious assumption (though it may be correct). In at least one such data set I recall looking at, helmet use was also associated with a reduction in arm injuries, where a causal relationship seems ridiculous. There are other differences between groups of people who wear helmets and those who do not, on average, and it is these confounding factors that make it impossible to determine causal relationships. The real problem here is that it is impossible to perform a true controlled trial where people are randomly assigned to either use helmets or not. I recall seeing a graph a while back showing the NHTSA statistics for injuries and/or fatalities of pedestrians and cyclists over a long time (something like 40 years, beginning in the early 1970s, I think). I believe it showed identical trend lines for both groups, despite the fact that helmet use had grown substantially for cyclists over that time, but not (obviously) for pedestrians. Again, not proof of causality, but it certainly doesn't support the claims that helmets reduce head injuries by 85% when it's not detectable in whole-population injury statistics. I would provide a link, but I can't find it just at the moment, I'm afraid. -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To view this discussion on the web visit https://groups.google.com/d/msg/rbw-owners-bunch/-/_02J-d0PYHcJ. To post to this group, send email to rbw-owners-bunch@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
