Cycle helmets are just polystyrene caps
Well yes, they are. Cycle helmets are thick pieces of compressible polystyrene with a slippery surface, just like motorcycle helmets. The slippery surface is designed to allow your head to slide along the road, rather than come to an abrupt halt, and the polystyrene is designed to progressively crush, ensuring your skull (and thus brain) decelerates more slowly than would your bare head. That's how helmets work, and polystyrene is used because it's very good at that job. Sure, cycle helmets are flimsier than motorcycle helmets, that's because motorcycles travel rather faster than bicycles do.
Cycle helmets don't work above 12mph
Yes, the polystyrene in a cycle helmet is designed to completely compress in a 12mph impact, and thus has no further part to play in a 13mph one. As most cycling accidents involve an impact of no more than 12mph, that is the speed at which they are required to pass tests of effectiveness. But in a 24mph impact, the helmet still absorbs 12mph worth of force. It is, for some accidents, better than nothing.
Walking is more dangerous than cycling
Statistically true, but only if you include toddlers and senior citizens, who account for the vast majority of head injuries from trips & falls while walking. It's not true for the majority of adults. Except when walking home from the pub.
Cycle helmets increase the risk of rotational injury
It's true that the real risk with head injuries is not the skin and skull, but what happens to the brain inside the skull. The argument about rotational injuries is that a helmet effectively increases the size of your skull, increasing the speed at which your head rotates when it hits the ground, and thus increasing brain injuries. There is some truth in this, but remember that slippery shell: that's designed to increase the likelihood of your head sliding rather than rotating. Hair and skin, in contrast, has very high coefficient of friction, making it more likely your head will rotate in the first place.
So, if I find some of the key arguments against helmets unconvincing, why then do I choose not to wear one? Three main reasons ...
Cycling is safe
Cycling is a very safe activity. Minor accidents are rare, major accidents are very rare. Statistically, it would make more sense to wear a helmet when driving a car, doing DIY or walking downstairs than to wear one while cycling.
A helmet is useless in most accidents
In a minor accident (eg. hitting a pothole on the flat and going over the handlebars), the risk of head injury is very low: you're much more likely to break a wrist, elbow or collar-bone. In a major accident (eg. being hit at speed by a car), the chances of a helmet affecting the outcome in any meaningful way is very low. Put these two points together: I'm unlikely to have an accident at all, and if I do, a helmet probably won't make a difference.
It's statistically irrational
Cycling is much safer than driving. Many more car occupants than cyclists die of head injuries, and an Australian study calculated that around 15% of them would have survived had they been wearing a cycling helmet. If you want to be rational about it, wear one in a car before you consider wearing one on a bike.
Helmets give a false impression of the risks
Helmets are worn for risky activities. By wearing a helmet when cycling, we add to the impression many non-cyclists seem to have that cycling is a dangerous activity. It's not, it's a very safe one. In fact, when you take into account the benefits of regular exercise from cycling, and the fact that heart disease is the biggest killer in the developed world, it's actually statistically safer to cycle than not to cycle. If we want to encourage cycling, we need to make it as approachable as possible, and part of that is not making a very ordinary activity look like a treck across the Andes.
Next time you're in one of the cycling capitals of the world - Amsterdam or Copenhagen, say - tell me how many cycle helmets you see.
www.benlovejoy.com/cycle/attitude/helmets.html
Taken from this website