My mother worked in a head trauma unit while I was young, and I particularly take umbrage with that last bullet point. While wearing a helmet won't do you much good when you ignore a stop sign and get plowed over by an SUV, neither will a seat belt save your life if you lose control going 110 down a tree-lined rural highway.
I'm rather shocked at the number of comments in this thread that just extrapolate anecdotes. Your mother's profession has nothing to do with this whatsoever, unless it involved studying the actual statistics of bicycle helmet safety.
Whether a bike helmet makes you safer has nothing whatsoever to do with statistics; it is simple physics. You can try it yourself by hitting your head with a rock--with and without the helmet on.
Right, and adding more programmers to a software project will always make it finish earlier (try it yourself by writing a small app with a friend), and flying is always more dangerous than driving (try losing your engines in an airplane and in a car).
No, it really is just simple physics. Arguing this point just makes it look like you don't understand the limitations of epidemiology.
Allow me to illustrate the fallacy with this joke: A man is arrested at the airport because he has a bomb in his backpack. When questioned by police he claims he brought it for safety because "what are the odds that there would be TWO bombs on the same airplane?"
Put another way: you don't need a population study to decide whether feeding rat poison to kids is a good idea.
Now if we were talking about whether mandatory helmet laws make people safer, population statistics are essential tools of policy analysis.
But if we are talking about one single head, we know the helmet increases safety based on the simple rock test I outlined above.
I thought we were talking about the population as a whole, not a single head. Not mandatory laws, but a culture where helmet use is de facto required versus not.
I also recall studies where wearing a helmet was found to be more dangerous overall, for the individual, because drivers assume that helmeted bicyclists are more skilled and don't give them as much room, leading to more accidents.
My point being that you can't simply take a simple "rock + head + helmet = better" and assume that conclusion is correct. This stuff is complicated. And everybody in this thread trying to pretend that this stuff is not complicated is really pissing me off.
Edit: to make sure we're not talking past each other, there are at least five different relevant questions here:
1. If wearing a helmet was required by law, would this be a net gain for society?
2. If wearing a helmet is heavily encouraged by society but legally optional, would this be a net gain?
3. Is wearing a helmet regularly a net gain for the individual?
4. Is wearing a helmet on one particular ride a net gain for the individual?
5. Is wearing a helmet in a crash a net gain for the individual?
The only question answered by your simple physics is #5, which also happens to be the least useful question in the list. Even #5 is not obvious the way you make it sound: it's entirely possible, although probably not actually the case, that the added weight increases the risk of neck trauma more than the protection of the skull reduces the risk of head trauma. In any case, none of the other four questions are answered at all by your thought experiment, even though those four questions are what we should be examining when we ask the question of whether we should wear a helmet while riding, and whether we should encourage or require helmets in general.
When I was a kid, my best friend's brother died because he was not wearing a bike helmet. I do, in fact, always wear a bike helmet.
The argument is not whether, if hit in the head, you are more likely to get a head injury. It is clear that bike helmets reduce those injuries.
The question is, if we required everyone to wear helmets, or required everyone to not wear helmets, which would result in less injuries/fatalities. And secondarily, if it turns out that bike helmets reduce injuries and fatalities, has it been worth the cost, vs other things we could spend money on, say legally required non-slip surfaces for bathtubs.
There are multiple factors that could affect this, here are two such things:
