You see these stories in the news all the time. A bicyclist gets hit by a car and suffers a major head injury. It could have been much worse, we are told, but thankfully he was wearing a helmet. A shattered bike helmet is shown, with the implication that this could have happened to his skull:
While pictures like this are scary and dramatic, they are actually further evidence that bike helmets are ineffective. This helmet did not function in the way it was intended. In fact, it failed spectacularly.
Let’s review the physics of a bike helmet. They are constructed out of polystyrene foam (styrofoam) which is supposed to compress in a collision. This compression spreads the force out and reduces the acceleration of the brain as it smashes into the inside of the skull. At least that is how it is supposed to work — under ideal laboratory conditions where the impact force is perpendicular to the helmet. Actual collisions are chaotic events involving complex interactions. When subject to an oblique impact, the styrofoam will typically crack and break off without compressing. This is what appears to have occurred in the helmet shown above. If there is no compression, then it is unlikely the helmet absorbed the impact.
What is unfortunate about these kinds of news stories is that they give false hope about the effectiveness of bike helmets. And rarely do these stories ever mention the dangerous road infrastructure that caused the crash to happen in the first place.
huh
ok
still rather have one than have head smack on concrete
exactly – while improving motorists’ awareness, and the cycling environment in general, are worthwhile aims, we have to cycle in the world that exists NOW, and as far as I’m concerned, even non-perfect protection is better than none
[…] что шлем раскололся. В действительности шлем должен сплющиваться, поглощая энергию удара, и тот факт, что он разбился, […]
Quite right and the evidence shows they don’t save lives. There are thousands of these “helmet saved my life” stories, but the death rate of cycling doesn’t drop as helmet wearing rates go up, so they can’t be true. https://www.cyclehelmets.org/1209.html
I was just sideswiped by a vehicle about a week ago; the result is that I fell hard onto a concrete surface. I have fractured ribs and a fractured clavicle. I have no way of knowing what might have happened to my head had I not been wearing a helmet. My head impacted the concrete reasonably hard, and I never lost consciousness, have no abrasions, and I’ve never had a headache. The helmet does have a hairline crack, and I’ll check to see if there are signs of compression. But even without signs of compression, the styrofoam is more forgiving and certainly less hard than the concrete surface I impacted. I believe the helmet did provide good protection.
I wasn’t taking unnecessary risks because I was wearing a helmet; I was simply riding my bike to get some exercise.
In spite of studies and opinions such as this, I’ll ride with a helmet every time.