Apr
15
2009

How do bicycle helmets make riders safer?

The helmet, an essential bicycle accessory. This photo was taken at Stanley Park in Vancouver, British Columbia. Troshy photo. CC-BY.

The helmet, an essential bicycle accessory. This photo was taken at Stanley Park in Vancouver, British Columbia. Troshy photo. CC-BY.

I remember bicycling in the streets of downtown Seattle, Washington, during the early 1970s feeling quite vulnerable to the traffic, so I became one of the early adopters of bicycle helmets, such as they existed in those days. There were no helmets made specifically for that purpose then, so the few of us bicyclists protecting our heads wore rock-climbing helmets — uncomfortable, heavy and unventilated, but they were capable of accomplishing the task well.

Fortunately, helmets for bicyclists have improved considerably since then: They’ve become lighter, the materials have improved, and the design allows for the use of holes that improve air flow without compromising safety.

Bicycle helmets help protect users from injury in two ways. First, they’re usually made of fairly rigid plastic foam that compresses slightly on impact, serving to moderate the impact to the head. Thus it is important that if you’re in an accident that protects you from the head injury to replace the helmet — in most models, the compressed plastic doesn’t uncompress, so its benefits become reduced in a crash. Second, helmets help spread the impact of the collision over a larger area of the skull, making the crash less likely to cause cranial damage.

How much protection the helmets can offer is still a subject of some debate, partly because much of the evidence is more anecdotal in nature than based on hard statistics. Various reports have said that the helmets reduce serious injuries by up to 85 percent, but tracking down objective support for such numbers is easier said than done. Even so, there are some statistics suggestive of the need for head protection:

  • According to the Bicycle Helmet Safety Institute, a careful bicyclist will have a crash on the average of once every 4,500 miles.
  • In the United States, about 700 bicyclists die in accidents each year, usually because of collisions with motor vehicles. Of those, about three-fourths die of head injuries.
  • Of the U.S. bicyclists who die in crashes, 97 percent aren’t wearing a helmet.
  • A study published in a 2008 issue of Clinical Pediatrics found that between 1990 and 2005 there were 6.2 million children treated in U.S. hospital emergency rooms for bicycle-related injuries.

The good news is that the price of helmets meeting safety standards has come down, and they’re easy to find. When buying a helmet, you should look for one that fits snugly, is comfortable (so you aren’t tempted to leave it at home), is light in color (to improve visibility) and doesn’t have sharp points that might get caught on objects during a crash or tumble. Helmets designed for skateboarders should not be used for bicycling, as they are designed to withstand a series of minor collisions and scratches rather than crashes at street-traffic speeds.

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1 Comment

  • Richard Keatinge says:

    Good scientists don’t “track down support” for ideas. The check whether the facts actually support the ideas. In the case of bike helmets, the figures don’t show that they work – helmet laws have stopped a lot of people cycling and have done nothing for head injury rates, see Robinson DL. No clear evidence from countries that have enforced the wearing of helmets. BMJ 2006;332: 722-5. http://www.bmj.com/cgi/content/full/332/7543/722-a. For comments on some of the stuff produced to support helmets, see http://www.cyclehelmets.org.

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