Riding a bicycle is a healthy part of being a child. But if a child is going to ride a bike, he should also wear a properly fitting helmet. In 2007, nearly one quarter of bicyclists who were injured in crashes with motor vehicles were 14 or younger.

Why wear a helmet?

A helmet can reduce the risk of serious brain injuries by as much as 85 percent. From 1990 through 2005, the Consumer Product Safety Commission estimates that more than 6.2 million children under 18 were treated in hospital emergency rooms in the U.S. for bicycle-related injuries. Despite the protection afforded by a helmet, only about 25 percent of children 14 and under actually wear them.

Among children, bicycling injuries are the leading cause of recreational-sports injuries treated in emergency departments. (See Tips for biking safety.) A bike helmet can not only save a life, but it can also prevent or lessen the severity of brain injury during a bicycle crash. Nearly half of children 14 and under who are hospitalized for bicycle-related injuries
receive a traumatic brain injury diagnosis.

Any helmet is better than no helmet, but to learn more about some widely available models for children, we tested 15 kids' traditional and multisport style (sometimes called BMX) helmets, ranging in size from those that fit infants to those that fit adolescents, and even some adults. Infants should only start riding and wearing a bike helmet at 1 year old, whether they are in a bike trailer or other kind of attachable seat. We don't recommend that a passenger younger than 1 ride in a bike trailer or other kind of seat. Children's helmets sometimes have fewer ventilation openings than adults', because children are often passengers rather than cyclists and thus sweat less. We indicate which provided better ventilation in the Ratings. Helmets we tested range in price from $18 to $50.

All the helmets we tested met the mandatory CPSC standard for "impact absorption," which mimics what happens to a person's helmeted head when it crashes into a curb, rock, or the ground. We also went beyond the standard and subjected the helmets to more force to see how they would perform, and the majority of helmets surpassed the standard and withstood the extra force. According to the standard, we also tested the helmets in extreme hot and cold temperatures, and under wet conditions meant to simulate sweat or rain, which can affect how well the helmets can protect your head. Two toddler models and one youth model scored Very Good for impact absorption in our Ratings. Those models also scored well for ease of use, making them top performers in our tests, and good values at $30 each.

We also tested the helmets against the CPSC standard for "retention-system strength"—how well the straps resisted stretching, slipping, or the buckle resisted breaking when a force was suddenly applied, such as what could occur during an accident. A good retention system will also allow you to achieve a snug fit, position the strap guides, and buckle the straps so that they're comfortable. A strap with a fixed length limits where the buckle and strap guides can be placed, and can affect comfort and good fit. Finally, we tested how well a properly fitted helmet resisted front to back and side to side movement to ensure that the helmet stays in place for the best protection. (See How to get a good fit.)

All helmets came with suggested ages or size labels that were appropriate, except for the Hannah Montana Denim, which was labeled "8+ years," but which we were only able to fit on a few kids who were older than 8 and even a few full-grown adults. It is available in a smaller size, but don't rely on labels—try it on the child to be sure the helmet fits properly.

We also looked for other attributes, such as whether the helmet buckle had a "pinch guard," which is a shielded buckle that helps to prevent pinching, whether it had an in-mold shell (an outer plastic casing that makes it easier to spot cracks or dings), how easy the various buckles and strap adjustments are to use, type of visor, and a warranty or damage/ replacement program. We also weighed the helmets, an important factor for young children whose necks might not be strong enough to hold up a heavy helmet for long. A lighter-weight helmet can cause less fatigue.