Question:
Tho pointed out that his head was hotter in a helmet than without one. In a study that the summary stated showed that helmeted heads cooled equally well to bare heads (note this Richard) the real information contained within the complete study showed that helmeted cyclists doing moderate exercise regimes in controlled conditions stated that their heads were hotter with helmets than without. The charts also showed that helmeted cyclists had higher heart rates than un-helmeted cyclists thereby backing up the claim of these cyclists.

You may also do a simple experiment. When you are cycling and sweat if pouring off of your head into your eyes, try taking off your helmet and riding bare headed. Does the sweat stop pouring into your eyes? Why would that be?

Answer: You speak of learning from others' accidents. I've had three friends killed riding in motor vehicles over the years. Within the last three years, two people I've known have had head injuries in cars - and both were belted in, one in a brand new SUV whose airbag worked as designed. His head injury was quite serious, causing months of missed work.

Now of course, the people I know constitute a small sample. It's much smarter to examine national data on head injuries, if you want to find out how safe the inside of a car is, or how dangerous a bike is. But then you find that riding in cars is by FAR the number one cause of serious head injuries, and bicycles aren't even on the usual lists.

Usually, at this spot, someone says "But people ride in cars more than they bicycle!" The obvious next step is to look at the per-hour figures. Per hour, riding a bike seems to be roughly twice as safe as riding in a car, and four times as safe as swimming.

If you (for some reason) don't want to count most of the gruesome, bone-crushing ways people die inside cars, and want to look only at deaths from nice clean head injury inside cars, the only per-hour figures I've been able to find claim head injury deaths per hour are the same for bikes and cars.