Whether bicycling helmet use should be mandatory is a heated topic, but helmets don't protect us from concussions, so experts are calling for radically new designs.
You're much less likely to suffer a severe brain injury if you're wearing a helmet, but your odds of sustaining minor brain trauma are similar with or without a helmet, studies show.
That's because modern helmets are lined with hard foam that can withstand serious impact, protecting your skull from fracturing against a hard surface. But the rigid foam doesn't absorb as much energy as a softer liner, such as those found in football helmets.
The best helmet for a cyclist would be made of a softer material thick enough to absorb any impact, but "nobody wants to bike around with a mushroom on their head," said Mehmet Kurt, who studies head injury prevention at the Stevens Institute of Technology in Hoboken, N.J.
The No. 1 reason people eschew helmets is self-image: how cool it looks or whether it will cause helmet hair, Kurt said.
Consumer preference has often driven helmet design, and not always toward safety. The transition from round helmets to elliptical or oval ones in the 1990s was "certainly not an improvement" safety-wise, said Randy Swart, director of the Bicycle Helmet Safety Institute.
But people wanted to look like Lance Armstrong.
A round helmet with a smooth surface is preferable, Swart said, because if a helmet snags during an accident, a rider's head will be whipped around, possibly causing a concussion.
Cyclists can sustain four types of brain injury: skull fractures, interior brain bruising and swelling, brain bleeding, and twisting or distortion of the brain, said Roy Burek, a visiting professor at the Concussion and Traumatic Brain Injury Prevention Group at Cardiff University in Wales.
Direct impact and linear energy can fracture skulls and bruise brains. Helmets protect from these injuries quite well. The hard-to-crack polycarbonate layer prevents skull fractures. Microscopic air pockets in the hard foam lining burst in a crash, allowing the lining to compress to about 25 percent its volume and absorb much of the impact that would send the skull smashing into the brain.
When a rider goes flying and skids to a stop, the brain experiences the effects of rotational energy, which can produce internal bleeding and contortion.
Helmets do a pretty good job of protecting riders from skull fractures and brain bruising.
They don't do much to prevent injuries resulting from rotational energy.
Swart envisions a smooth, round helmet with a softer material that survives more dramatic impacts but wouldn't need to be impractically thick.
Most bicycle accidents occur at low speeds, so an ideal material would be soft when you land at low speeds, to allow the brain to move, but also would be "smart" firming in a high-speed crash, thus preventing a skull fracture, Burek said.
Kurt said the most promising smart ingredient is air. He worked with Stanford University scientists to test inflatable helmets this year.
Collars that inflate like air bags when they sense a crash are available from the Swedish company Hovding, but they don't meet U.S. safety standards.
Bicycle helmets pose a unique challenge, though, because the impact speeds of a crash, especially with a car, can be much greater than those of colliding athletes. Kurt says he is "fairly optimistic" we could see a better bicycle helmet in the not-too-distant future.