Is it? For bicycle helmets I just know these variants: 1. Wearing a bicycle helmet is unpleasant, so people will cycle less and possibly use other modes of tra

Is it? For bicycle helmets I just know these variants: 1. Wearing a bicycle helmet is unpleasant, so people will cycle less and possibly use other modes of transportation such as cars. The risk of a traumatic head injury may decrease but this is offset either partially or fully by other health risks such as obesity. 2. Other road users in heavier vehicles (e.g. cars) perceive riders wearing bicycle helmets as less vulnerable, and so keep less distance when overtaking them, thus wearing a helmet increases the risk of collision. I don't think I've ever heard someone say they won't wear a bicycle helmet because it would make them personally drive more dangerously. I personally strongly oppose mandatory bike helmets. I think one of the reasons so many people own and ride bikes in my country (The Netherlands) is that we don't have mandatory helmets. Making helmets mandatory for people inside cars would also prevent or reduce head injuries (and indeed that is why they are worn by race car drivers) so if we ever introduce mandatory bicycle helmets here perhaps we can introduce mandatory car helmets at the same time, to ensure that people won't just take a car instead.