The Great Bicycle Helmet Controversy

A month ago we took a look at the history of bicycle helmets and data on their usage at various locations in Minnesota. But should a bicycle helmet by mandatory, or even worn in the first place? Everyone points to the original study saying they reduce head injuries by 85% or tells anecdotes about how a helmet “saved their life” without any actual evidence (and in fact a helmet is designed to destruct dramatically in a crash, a head not so much). But there are two sides to the issue, so it’s time to look at some of the controversy:

The original study itself may not be definitive

The original defining study on bicycle  helmet use was a 1989 study conducted in Seattle and published in the New England Journal of Medicine, which determined that helmets reduce the risk of head injury in the event of a crash by 85% . This is the number that gets repeated again and again, even appearing on boxes for helmets in the mid 1990s. The population was 235 bicyclists treated at local emergency room, with a control group of bicyclists treated that did not have head injuries.

However, the CDC and NHTSA have withdrawn their support of the study. The researchers themselves have revised their number to 69%. But in case you haven’t figured it out the real problem is a better population group would be bicyclists as a group, rather than bicylists who were unlucky enough to crash and need to go to the hospital. Indeed, these numbers fall apart when extrapolated from an individual in an individual crash to whether they actually make society safer.

A lot of data about the effectiveness on a population comes from Australia and New Zealand, where mandatory all-ages helmet laws provided a before and after data point. A study on overall head injuries in New Zealand show they continued a long, slow decline without a corresponding bump when the law came into effect. Head injuries sustained by kids (solid black) and adults (solid red) is plotted against bicycle helmet use (dashed).

I think the key is to say “If you crash, a bicycle helmet is beneficial”. And the “If” is significant. The indirect effects: risk compensation, a distraction from better initiatives like better infrastructure, and reducing the number of bicyclists through fear and inaccessibility or just because a rider doesn’t want to wear one reduces the safety in numbers effect seem to negate the technical benefits.

Simply put, humans have a tolerance for a certain amount of risk, and making things safer is offset by increased risk taking. Of course seat belts have this effect too, but in that case the direct safety benefit overwhelms any risk compensation, and overall motor vehicle safety trends bear that out. That’s not so clear with bicycle helmets, and safety trends are inconclusive. One study went so far as to objectively measure risk taking while wearing helmets (although there is criticism that the risk taken blowing up a balloon until it pops is may not correspond to taken bicyle a bicycle).

You also hear figures that 97% of bicyclists killed weren’t wearing helmets. Although it’s a good number to scare your kids into wearing them, a fair question is if a bicyclist that is conscientious enough to put on a helmet is the type that’s tends not to ride dangerously or even illegally. (Additionally that number is from 1994, newer numbers are in the 60% range). Although these two points seem contradictory, they could both be in play on different levels for different individuals. But how many of the 90% would have been saved if they had ridden safer or if we had more protected bicycle infrastructure?

Safer Riding and Better Infrastructure

Although a recent study debunked the idea that bicyclists break the law more than motorists, that’s not a reason to not educate kids on up about safe riding skills. I came within inches of hitting a bicyclist who had blown through a stop sign on a side street and crossed Lyndale Ave in Bloomington at full speed. Had I not been able to panic stop I doubt the bicycle helmet he was wearing would have helped much.

People think that if they convince people to put on a helmet they’ve done good without addressing the much more important issues of safe riding skills and infrastructure design. Helmets are next to useless in bicycle vs car crashes, and motorists drive more aggressively when they see a bicyclist wearing a helmet. One guy from the UK measured this and found motorists get 8.5 cm closer to a bicycle when the rider is wearing a helmet. What if we showed the same amount of concern about getting more suburban MUPs built, more 4-Lane Death Roads eliminated, more cycletracks as opposed to making sure bicyclists wear helmets? Bloomington’s reluctance to eliminate 4-Lane Death Roads has been a continuous source of frustration for me (the upcoming Portland Reconstruction notwithstanding). (Another article on Death Roads is here, and my updated article on Bloomington’s Death Roads and an article on Portland Ave reconstruction on North Star Highways.)

The build if for Isabella program advocates for safer bicycle infrastructure. Isabella wears her riding helmet, but it’s a lot more important to build protected bicycle infrastructure. As a resident of Bloomington nothing frustrates me more than opposition to even unprotected bicycle lanes, or paving the river bottom trails in order to give our Isabella’s something to ride on but a sidewalk next to a 4-Lane Death Road.

Comfort, Image, and “Helmet Hair”, and the Fear Factor

Simply put, many people will only ride a bicycle if they don’t have to wear a helmet due to comfort, image (the dork factor and the dreaded helmet hair), and bicyle helmets create a culture of fear and inaccessibility surrounding the sport. When Australia introduced mandatory helmet laws in the early 1990s, cycling trips declined by 30-40 per cent overall, and up to 80 per cent in some demographic groups, such as teenage girls. Back in the US, here are the results of my study with respect to Minnesota, although I found so few teenagers bicycling that I hesitate to make any conclusions.

If someone decides to drive a car (or beg their parents for a lift) instead of riding a bicycle, it creates all sorts of indirect externalities. Even if you limit it to health, as a whole bicyle helmets are probably more dangerous than not. Besides the health effects of not exercising, the safety in numbers effect, where the more bicyclists are the less danger to each individual there is, has been well documented.

Helmet hair” (CC BY-NC-ND 2.0) by Julianna Damer

Once of the best way to make bicycling safer is to make more bicyclists, so motorists get used to seeing them around. Even many Australian medical professionals assert this.

They have discouraged large proportions of the community from using their bicycles and probably have caused a much worse impact on our nation’s health by keeping people away from this kind of exercise than they have given benefit by reducing head injuries


While there is evidence of benefit to the individuals wearing helmets, there is also evidence of wider harm to population health resulting from the reduction in cycling

A study in Melbourne and New South Wales found that compliance with the law was met as much by non-helmet users ceasing to bicycle as by riders starting to wear bicycle helmets. The number of bicyclists wearing helmets rose from 2,910 to 4,363, but the total number of bicyclists fell from 9,193 to 5,892.

If you’re a helmet supporter, charts like this one look good as they show a noticable drop in head injuries. However, the problem is this is the aggregated total, not per capita. And such a drop can easily be explained by fewer bicycle riders as opposed to bicycle helmets mitigating head injuries.

The notion that you have a 100% chance of winding up dead if you don’t wear a helmet really distorts the risks involved in the activity. Something that requires protective gear, and if you want to be considered serious, skin tight special clothing as well creates the notion that bicycling is something you do on a racetrack, not a reasonable way to get to the store or a friends house. To put it visually, suppose we make a comparison of stereotypical bicycling in the Netherlands vs the US…

Bicycling needs to be accessible to all. Building nice lanes and trails won’t help if we create a culture of fear around the sport, require uncomfortable and expensive gear, make it seem like not something to be taken lightly.

Helmet use is generally incompatible with bike sharing

Look at this chart.

Minneapolis may be towards the bottom because the climate is considerably harsher than the other cities and bicycling less established, but the bottom two cities have mandatory helmet laws and the rest do not. Rental or “disposable” helmet vending machines have been invented in response, but beyond discouraging usage this adds to the expense and complexity of running the programs. If anywhere you’d think bicycle sharing would be successful in Seattle, but their Pronto bike sharing program was shuttered due to low usage, and Seattle’s helmet law got a lot of the blame despite eventually offering bicycle helmets along with the bicycles. The helmets offered were “urban style” hard shell, which while subjectively more stylish are also more uncomfortable than higher end micro-shell helmets, and you also have the issues I listed above about perceived danger and accessibility come into play.

I did gather specifics on Helmet Use for Nice Ride users in Minnesota. Note the scale of the graph: 0%-14%, as opposed to scales approaching 100% on my other graphs. I didn’t gather data for Nice Ride for specific locations except for the Stone Arch Bridge. Factoring out the Nice Riders, helmet use increased from around 50% to around 60%, more typical of elsewhere in Minneapolis.

A reasonable conclusion for all this is that as an individual you might be safer in a helmet provided it does not induce you to ride less safely in other respects.  The benefits are not as great as portrayed, and since all of life involves risk of some sort, and the risk of bicycling isn’t that great. Bicycle helmet use should be an individual choice rather than forced to by laws or societal pressure.

About Monte Castleman

Monte is a long time "roadgeek" who lives in Bloomington. He's interested in all aspects of roads and design, but particularly traffic signals, major bridges, and lighting. He works as an insurance adjuster, and likes to collect maps and traffic signals, travel, recreational bicycling, and visiting amusement parks.