Originally Posted by
PeteHski
I agree, totally inconclusive and a pretty dumb hypothesis to begin with. I'm going to guess it was undertaken as part of some anti-helmet mentality on the part of the researcher. It's certainly been cited by that brigade many times since!
According to the paper I linked to, he was actually primarily testing the effects of different lane positions, and just threw in this variable out of curiosity (don't think I've ever seen that admission in a scholarly study!). The reanalysis showed that any supposed helmet effect disappeared in the 3 foot from curb position. The statistical argument is over whether a small difference in average passng distance matters when there's evidence that the average passing distance is over 3 feet or right around that much.
What no one seems to be addressing is that although this study involves thousands of passes, it's really a case of n=1 because they're all the same rider riding in the same general area. I don't believe that riders are uniform in any number of possibly relevant factors, nor do I believe that drivers behave the same in different contexts. I have no idea how the habits of drivers in Bath relate to those of the rest of the UK let alone to the US.