In fact, wearing a helmet does a lot more harm than good. It makes cycling look dangerous when it isn't and there is even evidence that cars tend to drive close to bikes with a helmeted rider.
Of course, if you're going out mountain biking or take part in a race, you'd be pretty stupid to do it without a helmet. But if you want to cycle to work or go down the shops, then it's really not necessary or desirable.
And if you're unfortunate enough to find yourself under the wheels of the truck, a helmet wouldn't have helped anyway.
Helmets and the Law in the British Medical Journal
Bike helmets can't prevent brain injury
The Bike Helmet Paradox
How bike helmet laws do more harm than good
The unintended consequences of bike helmets
This was also pointed out in 2006 study.
Ditching bike helmet laws better for health
People should wear helmets when cycling - a fallacy
To encourage cycling, lose the helmets
Sarah Wilson on helmets
Guilty Until Proven Helmeted
And a few figures...
An example for the helmet fallacy:
"Our response when someone supports Mandatory Helmet Laws just because they say a helmet saved their life one time:
Image shows/represents damaged ww2 aircraft that made it back from bombing raids. It's used to signify a fallacy... Military first thought they should protect the damaged parts of the plane. But in reality, the planes that didn't make it home were damaged in the white parts."
Thanks to @BicycleLobby and @Schmucklevision.
