A bicycle helmet is a helmet intended to be worn while riding a bicycle．They are designed to reduce impacts to the skull(头颅骨) of a cyclist in falls．However, there is a debate on whether helmets are useful for road cyclists．
The World Health Organization promotes the use of helmets as a strategy for preventing people' s heads from being injured by bicycle crashes or falls．Use of cycling helmets is supported by numerous groups in the United States. US-based cycling activist John Forester suggests that helmet wearing could prevent 300 deaths a year in the United States out of a total of 1530 preventable deaths．Public Health Law Research reports that there is enough evidence to establish that bicycle helmet laws are an effective public health intervention(干涉)aimed to reduce the number of head-related deaths．Received opinion in some countries is that bicycle helmets are useful and that every cyclist should wear one. Professional bodies elsewhere have agreed, such as the Swiss Council for Accident Prevention．
Mayer Hillman, a transport and road safety analyst from the UK, does not support the use of helmets, reasoning that they are of very limited value in the event of a collision（碰撞） with a car. He compares it to drawing conclusions on whether it is worthwhile to buy lottery tickets. Cyclists' representative groups complain that focus on helmets diverts(转移) attention from other issues which are much more important for improving bicycle safety, such as road danger reduction．The UK's largest cyclists' organization, the CTC, believes that the "overall health effects of compulsory helmets are negative.'' The same report estimated(估计) that universal helmet use would save the life of one child aged 0 to 15 each year．
Up to now, the debate is with no consensus（共识）, but an organization has published a review of studies in 2011, saying there is a good deal of evidence that those wearing a helmet are more likely to crash than bareheaded cyclists．
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