Hjälmlagar har mycket liten effekt. Fortfarande är man inte helt säker på vad det beror på, men en sannolik förklaring är att försiktiga cyklister slutar cykla.
The results of this study indicate that the lacking effect of helmet legislation most likely has to do with a population shift effect, in which the introduction of mandatory bicycle helmet wearing will lead to a decrease of traditional cyclists in the cycling population, who do not have much accidents anyway, whereas the speed-happy helmet- and equipment using cyclists will remain. Reduced cycling will quite clearly have negative social health consequences (Cooper et al., 2008; Gidske et al., 2007; Hendriksen, Simons, Garre, & Hildebrandt, 2010). Reduced cycling may also lead to a reduction in what is called safety in numbers, i.e. the fact that the fewer pedestrians or bicyclists there are, the higher is the accident risk for these road users (Jacobsen, 2003). http://www.sciencedirect.com/science/article/pii/S1369847812000587