"To Lyndon Wade: Possibly they started out wearing the helmet but it became hot and uncomfortable so they sensibly removed it. Possibly part of their journey will be off-road where the chances of a fall are greater and there is at least some evidence that a helmet can do some good. Possibly they are on their way to an organised event where a helmet will be mandatory but do not wish to wear it on the road. When I used to race in evening events at Hillingdon I would always carry my helmet strapped to my back pack when I rode to and from the event. I would have raced without it if I had been allowed to.
Cycling is no more dangerous than walking and is not particularly productive of head injuries so the people who choose to wear helmets while cycling on the road are not in very great danger. But the most reliable evidence is that they are marginally more likely to sustain a serious or fatal injury than those who do not."