From what he says, it's not clear if the frontal lobe damage was from hitting the road, or rebound from the initial impact. But anyway it clearly indicates that a helmet isn't complete protection.
What would really have happened if he hadn't been wearing a helmet? Would the blow have dashed out his brains? Would a sharper impact have put more of the energy into damaging the wing mirror? Would the blow have connected as solidly or at all? Would the truck driver have given him a wider berth if he'd looked more vulnerable?
From what he says, it's not clear if the frontal lobe damage was from hitting the road, or rebound from the initial impact. But anyway it clearly indicates that a helmet isn't complete protection.
What would really have happened if he hadn't been wearing a helmet? Would the blow have dashed out his brains? Would a sharper impact have put more of the energy into damaging the wing mirror? Would the blow have connected as solidly or at all? Would the truck driver have given him a wider berth if he'd looked more vulnerable?
I still choose not to wear a helmet.