Originally Posted by charles vail
I am not convinced that the current styrofoam bicycle helmets are any help at all and in fact they may cause neck injuries upon hitting the road. A old school hard shell hockey helmet would probably be a better helmet for cyclists provided it had enough ventilation.
Its kind of interesting that elite runners run as fast as many cyclists average speed and nobody seems to be worried that they might trip and fall and crack their head.
Then of couse there is the cooling effect when hill climbing, of not wearing a helmet. Anybody ever wonder how many cyclists fall over due to heat exhaustion, while wearing their helmet? 
If you were to see it anywhere, you'd see someone falling over from heat exhaustion on the Tour de France. So far, in the last two seasons, I haven't seen that reported. This has more to do with keeping ahead with your fluids then whether or not the person was wearing a helmet.
John