Translation (TZ): The figures given by Burton seem to me confusing in some minor parts of the study. The main conclusion is sound, as far as I can see. Nevertheless, I'd like to comment on these details: In graph 14 the percentages are taken with respect to all people in the study. However, the three groups wear helmets always / sometimes / never differ largely in size. Therefore, it is trivial that the blue bars are the highest. I would recommend to take the percentages relative to th