Helmet Data

Lots of people wonder whether helmets work to save lives, whether they are better for kids than adults, whether they all work the same, whether they are worth the cost to the purchaser or to the society...  I'm not going to even try to answer those questions myself but I'll show you where to look for them.

First of all, we ourselves strongly prefer to wear helmets whenever we ride, but other people feel that cycling is safe enough as it is, like walking, and don't see the need for one. That's fine, too, especially for adults who are making the decision about their own risks and benefits. Nobody is wrong, in our view, though many people seem to demonize those who disagree with them. One of our favorite studies showed that like many cyclists, even neurosurgeons in Germany are divided.  Link is here. 

Really, the best time to wear helmets might be during a discussion with other bicyclists about helmets.

Although cyclists are very divided on this issue, it is only rarely that you see the actual research on it. So here it is! This is a sampling of some data we've found and some ways to get related sources. The links go to the full article if possible, or to an abstract otherwise. Often you can link to the full article from the PubMed medical database abstracts, from the top right side of the screen. Or go to www.pubmed.com and type in a query like bicycle helmet injury risk for a very complete list. PubMed covers nearly every article worldwide that's important to the medical and medical science research community. Other sites on ncbi.nlm.nih.gov cover more basic science and probably don't have much on bikes. Google is less useful but try it if you want.

To summarize the issues (paraphrasing):

Helmet supporters argue that:
     helmets reduce the severity of injuries and save lives of people who would have died of their injuries
     This reduction in risk is usually cited as between 65-90 % and is repeated in many studies
     kids in particular can benefit from this
     helmets are effective for preventing injury, no matter whether it's a crash with a car or with a tree or another rider

Helmet law supporters argue that:
     Because they are so convincingly protective, helmets should be mandatory for every rider, or at least for children.

Helmet detractors argue that:
     Riding a bike isn't that dangerous compared to other things and you don't need a helmet, based on your low risk of injury
     Neither do kids need a helmet, for the same reasons
     Helmets decrease bike ridership and make biking seem more dangerous than it is, and when there aren't as many riders on the road each one is less safe
     People with a helmet take risks they wouldn't try if they were bareheaded
     Few riders in Europe use them and they have low risk of injury
     There are a lot of other more important factors than just helmets that affect bike safety

Helmet law detractors say:
     The number of bike riders goes down when a helmet law is introduced
     This cuts down on the general health of a population and/or brings costs
     There is no compelling reason for the State to mandate helmet use and limit individual decision making

The Research (some of it):

Newest available US fatality statistics 
Insurance Institute for Highway Safety - Highway Loss Data Institute 

Summaries of multiple studies from a helmet supporter:
Harborview Injury Prevention and Research Center

The seemingly most cited article in a medical journal (found 85-88% risk reduction):
A Case-Control Study of the Effectiveness of Bicycle Safety Helmets

Cochrane intervention review (same authors) (2/3 risk reduction):

Another summary:
Systematic reviews of bicycle helmet research

I found articles quickly from Finland, Sweden, the Netherlands, Germany, Britain and Australia, some below. Eastern European and Asian studies of bike injuries are also generally on PubMed, with at least an abstract in English.

Cyclist Injuries Treated in Emergency Department (ED): Consequences and Costs in South-eastern Finland in an Area of 100 000 Inhabitants. 

Clinical factors associated with intracranial complications after pediatric traumatic head injury: an observational study of children submitted to a neurosurgical referral unit. 

A decrease in both mild and severe bicycle-related head injuries in helmet wearing ages--trend analyses in Sweden. 

Comments on Depreitere et al. Lateral head impacts and protection of the temporal area by bicycle safety helmets. J. Trauma. 2007;62:1440.

The current injury situation of bicyclists--a medical and technical crash analysis. 

[Bicycle accidents in children in The Netherlands in 1990/1991; time for bicycle helmets]

[Bicycle accidents. A retrospective study 1986-1991]

Bicycle helmet legislation: can we reach a consensus?

The efficacy of bicycle helmets against brain injury.
(search for this author for more articles)

Three lessons for a better cycling future

Arguments against helmet legislation are flawed

Again, this is just a small sample of sources we've been reading lately. Link to PubMed and have a look for yourself! Maybe after looking at the statistics and research you'll begin to see the rationale of the other side's opinions, or at least have more ammunition for your next squabble...


  1. First off, I always where a helmet. I truly believe they can prevent major head trauma in most cases, although I understand the possible neck torsion injuries that could also accompany a crash. I'm undecided on the other non-medical issues that come up on this topic.

    The problem I see here is that most people don't really understand the physics behind a typical crash. My brother-in-law is an engineer for GM - he understands inertia and momentum and often performs complex crash simulations. One day he showed me a rendering of an accident - the situation involved placing a case of beer (unrestrained) behind the drivers seat during a low speed (60km/h) head on collision. You'd be amazed at the damage but I can guarantee you that many of us have done the same or similar.

    So why would GM perform this type of simulation? Because people unknowingly do stupid things! Here's another example - people who choose not to wear seat belts. Again my brother-in-law explained that a head on collision at low speed (between 40-60km/h) is the equivalent of doing a belly flop from the second story. My math may be wrong but you get the idea. Now why would a person who chooses not to wear their seat belt agree to jump from a 2nd story building? They wouldn't. But that doesn't stop people from not wearing their seat belts.

    That's all I have to say on the matter...

    1. People not understanding physics.....ok....how about the fact that no matter whether you are wearing a bike helmet or not, if your head decelerates from 20mph to 0mph your brain will still be travelling at 20mph (or thereabouts briefly) it will impact on the inside of your skull giving you a concussive injury, regardless of what you wear.

  2. We also wear helmets and in most states in the U.S. children are required to wear helmets so it isn't an option to let our kids go helmet free.
    Here in Chicago also riders are for the most part without many options but to ride in traffic.

    Colville Anderson's position on helmets has obviously had a big impact among transportation riders here in terms of the helmet discussion. Not to advocate either way, we do wear helmets and for the most part ride in plenty of traffic even on quiet streets. A photo at one of this year's MBAC meetings portraying a Mom riding carefree down the Kinzie Lane with an also helmet free toddler in her Ibert was interesting from my point of view mostly because of CDOT using the slide when they are bound by the state helmet law as well. I also had an interesting experience last year leading a Kidical Mass ride at the Cyclelogical event near Clarendon Park. Interestingly a couple rode with their less than eight month old daughter in their I love CPH stickered box bike-- none of them in helmets. After a long time riding with all of my kids in traffic in Chicago I was curious about both decisions- to show and to ride with a young child who cannot make their own decisions about how to be safe in our urban riding environment.

    Note that riding the Kinzie lane until the recent changes on Wells would dump you out is a totally busy traffic area with barely a lane around in any direction. The new buffered lane on Wells is buffered by paint and spares no rider from the usual decision to either ride in the door zone of the cars on the right or get sandwiched by the moving drivers on the left regardless of the paint.

  3. Why don't we require children to wear helmets in cars? Or adults for that matter?

    Why do we allow them to play football (about 7 times the death and injury rate as riding a bike without a helmet) or be cheerleaders (about 5 times the death and injury rate as riding a bike without a helmet)? Or soccer, hockey, swimming, diving, ...

    Making helmets an issue is quite irrational given the much greater risks out there. Like obesity.

  4. As an RN with over 30 years of experience in areas such as ER, ICU, rehab, and pain management, my observation is that when I see someone who has been involved in a bike accident who was not wearing a helmet, a head injury is usually present. A few years ago, I cared for a 32 man who had just graduated from an MBA program at a prestigious college - smart guy! He was riding his bike, on his way back from a graduation party, when he was struck by an elderly woman who did not see him. He had no other injuries except for a severe traumatic brain injury. After caring for him for over 2 weeks, during which time he had several emergency trips to neurosurgery, he died. May have been smart, but lacking a helmet killed him. Unfortunately, he is only one of the many I've cared for.

    On a personal note, on my to work in 2008, while riding on a local bike path, I was involved in an accident due to another person's inattention. I landed on my head. While I sustained a number of nasty, and to this day still painful, cervical disk injuries, had I not been wearing my helmet, I would have been dead...very dead.

    I can't encourage people enough to wear helmets. It makes sense...at least to me.

  5. Not only do I not wear a helmet, I also usually have headphones on. That's not to say I'm totally oblivious to what's going on around me, far from it! In Michigan, it's legal to ride a motorcycle without a helmet so requiring a bicycle rider to wear one would just be asinine. And even if there was a law mandating it, I wouldn't. I'd much prefer the car driver that hits me to lose his/her license permanently whether via court mandate or a result of the lawsuit I'd win that would remove the person's financial ability to own a car.

  6. Thanx for the info!
    I recommend purchasing the foldable helmet Fuga by http://www.closca.co

  7. Is there any credible study about whether helmet wearing attracts more accidents towards the head?
    My own guideline, cycle in a way that I don't need a helmet for protection. When a helmet is needed, it is too late and there are many other ways that can end my life, or make the remaining part of my life very painful.

    1. Well, there is a lot of skewed information on the Internet I'd suggest again using pubmed.com as a search engine for peer-reviewed sources. However, while riding sensibly to avoid accidents is always a good idea, it doesn't keep the drunk guy driving home at 10 am after a night out not sleeping from running a red light and crushing you. He'll be fine in his pickup but you have a much better chance, I tthink the available evidence shows, if you are in a helmet. It's a personal choice that you, like everyone, can make on your own.


We encourage anybody to comment on Chicargobike. But please don't put advertising (or a link to it) in your comment or name or it will be removed. Too much spam has led to us having to moderate your comment before it's posted. It might take a day or two. Sorry.