Hugh Pickens writes in about the detrimental effects of mandatory helmet laws (at least as applied to adults): "Elisabeth Rosenthal writes that in the United States the notion that bike helmets promote health and safety by preventing head injuries is taken as pretty near God's truth but many European health experts have taken a very different view. 'Yes, there are studies that show that if you fall off a bicycle at a certain speed and hit your head, a helmet can reduce your risk of serious head injury,' writes Rosenthal. 'But such falls off bikes are rare — exceedingly so in mature urban cycling systems.' On the other hand, many researchers say, if you force people to wear helmets, you discourage them from riding bicycles causing more health problems like obesity, heart disease, and diabetes. Bicycling advocates say that the problem with pushing helmets isn't practicality but that helmets make a basically safe activity seem really dangerous, which makes it harder to develop a safe bicycling network like the one in New York City, where a bike-sharing program is to open next year. The safest biking cities are places like Amsterdam and Copenhagen, where middle-aged commuters are mainstay riders and the fraction of adults in helmets is minuscule. 'Pushing helmets really kills cycling and bike-sharing in particular because it promotes a sense of danger that just isn't justified — in fact, cycling has many health benefits,' says Piet de Jong. 'Statistically, if we wear helmets for cycling, maybe we should wear helmets when we climb ladders or get into a bath, because there are lots more injuries during those activities.'"