Halloween costume helmets

"Cape does not allow wearer to fly."

This label, off a kid's Batman costume, has been circulating on lists of stupid warning labels for at least a decade before Batman Begins, which was the first time I can remember anyone actually showing Batman using his cape to actually fly. With Halloween costumes showing up in every Wal-Mart now, it's time to address a similar type of costume that's sold in bike shops year round, the novelty helmet.

Novelty helmets do have their place - as costumes on the set of a movie, or in a play, or yes, as a Halloween costume. They don't really make much sense on your head on a public road. Your average bicycle helmet provides more protection than a novelty helmet.

Unless you've wandered into a very unscrupulous motorcycle shop, they're easy to spot in the shop by the lack of a DOT approved sticker on the back, and often by a warning label inside it that it's not a real helmet. If you look closely, you can spot them on the road much of the time - they're very thin compared to a real helmet. It's a dead giveaway. There are a couple of somewhat thin, legal helmets, such as the Davida Ninety-One, but engineering a thin helmet that actually protects the head inside it is a major challenge. And many of the novelty helmets you see out there are about a quarter of the thickness of the Ninety-One.

To understand the problem with making a helmet thin, imagine that you've got a choice of diving off the roof of your house onto (1) a stack of four matresses, or (2) a concrete driveway. Assume it's just as far to either one. Obviously, the stack of matresses is going to hurt a lot less than the concrete. The reason a soft object is going to hurt less is that it compresses more. As a first approximation, if that stack of matresses compress 100 times more than the concrete, it'll only have to push you 1/100th as hard to stop your fall. The amount of crash (kinetic energy, if you want to get techincal) the helmet can absorb is equal to the force it pushes back on you times the amount of distance your head can push it. A real, DOT approved helmet is often ten times as thick as a novelty helmet... meaning if you smack your head into concrete wearing it, that novelty helmet is likely to give you ten times the hurting.

I'm a bit puzzled about why people wear novelty helmets on the street. Is it cost? That doesn't make that much sense, as you can get real helmets for only a couple more dollars. Comfort? Not if you've chosen the helmet correctly; the companies that make the good helmets put a lot of R&D into making their products fit comfortably. Style? That may be it. The thing is, what you put on to ride your bike isn't just what everyone sees; it's the only thing between you and that 10,000 pounds of steel hurtling towards you at over a hundred miles an hour in the other lane. It's not a fashion statement. It's not your costume. It's your armor.