Bicycle helmets
Last updated: November 11, 2009.
You've seen those amazing, Olympic cyclists leaning forward,
crouching, head-down into a snug, aerodynamic position to shave every
possible second off their time? The only real problem is if they hit
something and crash. Riding with your head so far forward means it's
much more likely to bear the brunt of the impact when you smash into
the road. Head injuries are really bad news. According to the US
Consumer Product Safety Commission: "About 900 people, including
more than 200 children, are killed annually in bicycle-related
incidents, and about 60 percent of these deaths involve a head
injury." Thank goodness, then, for bicycle helmets. Like your
favorite candy, they're hard on the outside and squashy in the
middle—and that two-layer design helps them absorb impacts and save your life. Let's
take a closer look at how they work!
Photo: When cyclists lean forward to create a more aerodynamic shape, it automatically puts their head at greater risk of injury in a crash. That's why wearing a helmet is important. Photo by Christopher D. Blachly courtesy of
US Navy.
How does a bicycle helmet work?
At first sight, a cycle helmet looks much like any other hat, but look more
closely and you'll see a lot more thought—and science—has gone into
the design. A typical helmet has two main parts: a hard outer shell
and a soft inner liner. The hard shell is designed to spread the
force of an impact over a broader area so your skull is less likely
to fracture, while the soft liner is meant to squeeze inward and
absorb the impact energy, so less of it is transmitted to your head.
Bicycle helmets are a good example of how the right material can make all the difference to
how well something does its job. Shells are typically made of composite materials like fiberglass or
lightweight carbon fiber, or very hard plastics such as polycarbonate
or ABS. Liners are usually about 20cm (0.8 inches) thick and made of
two layers of foam: a soft, bouncy layer that absorbs small bashes and
bumps and a stiff layer that permanently deforms to absorb very hard
impacts. Some helmets are now incorporating energy-absorbing plastics like
d3o that are soft in normal use but harden instantly
the moment you hit them, but most still use cheaper and simpler
materials like expanded polystyrene (EPS) foam.
Photo: How a helmet saves your life: When you bump your head, the hard outer shell (black) spreads
the impact over a wide area. The whole of the soft inner liner (orange) then absorbs the energy evenly so (hopefully)
there's minimal damage to your head. Without the helmet, the entire impact would be concentrated on a tiny part of
your head, very likely fracturing your skull and quite possibly damaging your brain too.
What's the best bicycle helmet to buy?
The best helmet isn't necessarily the one that looks cool; it's the one you're
most likely to wear. If it looks brilliant but feels uncomfortable or
gets too hot, you're less likely to keep it on your head—so it's a
waste of time. The most important things to think about when you buy
a helmet are:
- Does it fit snugly and stay properly in position on your head?
- Is it light and comfortable?
- Does it have enough ventilation holes so it stays cool?
- Do you like the look of it and will you actually wear it?
- Does it meet the latest consumer standards?
It may sound strange, but the last one of these is probably less important than the others:
the best helmet in the world is no good at all if it's too hot or
uncomfortable for you to keep it on your head. But assuming you find
a helmet that fits, looks good, and you're definitely going to wear,
make sure it meets the toughest test: that's the US Consumer Product
Safety Commission (CPSC) bicycle helmet standard. There are other,
lesser standards you don't need to bother with. If a helmet doesn't
meet the CPSC standard, don't buy it.
Photo: The best helmet for you depends partly on how you ride. Some BMX riders prefer ones
like this, which are more like climbing helmets, and don't have air vents. You're guaranteed to crash if
you do this kind of riding so a helmet is really, really important. Photo by Brock A. Taylor courtesy of
US Navy.
When should I replace a helmet?
You can buy a new helmet anytime you get sick of your old one, but
you must always buy a new helmet if you have a crash. If you
crack your helmet or compress the foam, it's not going to work
properly the next time—so get rid of it! For the same reason, never
buy secondhand helmets in thrift stores, from friends, or on places
like Web auction sites; you don't know what they've been through already
and whether they're still going to give you the protection you need.
Do I really have to wear a helmet?
People used to think bicycle helmets were uncool, but that's all
changed now. You won't find any professional cyclist racing on the
road or a track without a helmet clamped firmly to their head. And
helmets are so much better than they used to be. Have you noticed how
cool Olympic cyclists look in those teardrop-shaped chrono hats?
Virtually all modern cycle helmet are amazingly swish and can make
even the slowest of riders cut a dash. One word of warning, though. Everyone wants to look good,
but remember that a cycle helmet is primarily about protection.
Fussy, elaborate extras are usually just marketing gimmicks—so don't
waste your money.
There is an argument that helmets don't make as much overall
difference to how many people are killed or injured in bicycle accidents as you might expect.
People who study the psychology of risk point out that if
we make ourselves feel safer (with helmets on bicycles or seat belts
and airbags in cars) we ride or drive more dangerously and put
ourselves at greater risk of an accident. That may well be true. But
if you're an ordinary, careful rider and you just happen to have an
accident, a cycle helmet will almost certainly reduce your risk of a
serious head injury and could well save your life. So remember: wearing a helmet
is a no-brainer; not wearing one could leave you with no brain!
Photo: A bicycle helmet must fit properly and be worn the
right way (low on your forehead) if it's going to be of any use at all. Poster courtesy of U.S. Consumer Product Safety Commission. See the full-sized version.
Further reading
Photo: An aerodynamic chrono helmet being worn by a triathlon rider. The teardrop shape reduces
air resistance around the rider's head. Photo by Suzanne Day courtesy of
US Air Force.
