My kids think I'm hopelessly uncool, and it rubs off on them by default.

The issue is bike riding. They're not allowed even to go down the driveway until they have their bike helmets firmly snapped onto their heads.

They hate it, because few of their friends wear helmets. Although I spend a good portion of my time trying to make sure I don't embarrass them on school trips or when kids come to our house to play, I don't really care that they think I'm awful when it comes to this topic.

In college, I had a friend named John. He was an avid hiker, a climber, a mountain biker who was among the fittest people I ever met. Like most people back then, he never wore a helmet.

He was coasting down the Avenues in the 1980s when a car turned in front of him, and he lost control while trying to avoid it.

His injuries didn't kill him outright. As far as I know, he's living still, but after months in the hospital and rehabilitation, he went to live with a sister elsewhere and, over time, I lost touch. But he was severely changed, and doctors at the time said most of the damage would likely be permanent.

He lost most of his vocabulary and the ability to speak easily and clearly, which made it difficult to tell how well he could reason. He had little control over his muscles and movements; independent mobility became a memory, although possibly not his.

I'll never forget looking at his skinny legs, shriveled from lack of use, or the grimace that stayed on his face.

If my children want to ride their bikes without helmets, they'll have to wait until they're living on their own. I'll nag at them so consistently they'll be likely to choose helmets simply for the joy of shutting me up.

I'm not alone in my zeal, by any means.

After the state health department released its most recent statistics on traumatic brain injury, I got a note from a physical therapist, Lloyd W. Shell, who has seen up close many brain injuries.

His profession often refers to traumatic brain injuries — TBIs — as "injury by stupidity." He often calls it "injury by adrenaline poisoning," he wrote. "By far the hardest to see/treat are the young ones. The senseless waste of a life that could have been productive but is now only a burden on those who will care for them. Wish I could get every teenager to understand what they are risking every time they do something stupid behind the wheel in the interest of 'fun.' Wish I could put every mid-20s bullet bike rider in flip-flops and a T-shirt in a wheelchair for a day to see what they risk."

There's no one who stands as firmly about safety gear as someone who has seen what can happen if things go wrong.