I don't wear helmets much, but that 'study', which has been discussed countless times here in BF, is so full of holes it makes swiss cheese look like a wall of titanium. I think the best conclusion that can be drawn from it is that if you look 'different' and unpredictable, drivers probably give you a wider berth.
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"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey