Im not so sure. It seems common sense to me that if there is a risk of banging your head, then you should wear a helmet. To make an analogy, if I trip up and scrape my knee in shorts vs jeans, then even though jeans are in no way regarded as safety clothing, the injury would be a lot less.
Of course John, there can be no disagreement on that.
But where does it stop?
As Frank inferred earlier, any case for helmet on cyclists founded on such trivia is equally valid for pedestrians, especially if they ever run at speed, as kids often do, and occasionally adults.
Some weeks ago I was cycling at 15 mph along the approach road to home when two of the local 13 year olds came running up from an angle across a side road, two kerbs and a rough grass ridge, just to beg a try on my bike. They had to running much faster than I was cycling to catch up, and on the obstacle course they covered, were much more at risk of injury than I was on a smooth road surface.
So they should be wearing helmets?
Of course not, for what I illustrated is just another "what if" situation. It's a tactic beloved of the nanny state types who, not content with their own sad inadequate lives, wish to run others lives for them.
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