Will Bicycling to Work Get You Killed?

Bicycle commuting is on the rise, as evidenced by the following articles in Treehugger.com, the Boston Herald, and USA Today. But if the idea of hitting the road on two wheels — with little to protect you from cars and trucks but good manners — strikes you as pretty risky, you aren’t so far from the mark.

Per kilometer, cyclists are 12 times more likely than car drivers to suffer a fatal accident, according to Rutgers University urban planner John Pucher and Lewis Dijkstra of the European Commission (the same study found traveling by foot to be 23 times more dangerous than driving, per kilometer). To put this finding in perspective, there were 785 bicycling fatalities on American roadways in 2005, compared to 4,881 pedestrian and 43,443 automotive fatalities that same year.

On the other hand, a Danish study found that people who do not bike to work suffer a 39 percent higher mortality rate than those who do. So, assuming you can avoid a fatal accident on the road, biking to work may actually help you live longer.

The risks associated with cycling decrease dramatically when more cyclists are on the road, and especially when those cyclists obey traffic laws. This second point is hammered home in this bizarre but brilliant 1963 bike safety film, “One Got Fat” (the eagle — or is it monkey? — eyed among you will have recognized a clip from this film in the Freakonomics video “Does Sport Cause Crime“).

One thing “One Got Fat” doesn’t mention is helmet use — helmets weren’t widely used until the 1970s, and controversy remains over how effective they are in reducing bike fatalities. (Full disclosure: I bike to work whenever possible, and wear a helmet, an adherent to what a few cyclists I know like to call the Cult of the Styrofoam Talisman.)

So, Freakonomics readers, just how effective are bike helmets?


As someone who managed to smack a bike into a curb, flip three times in the air, land squarely on my head, fall onto my back only to have the bike land on top of me....

Yes, that was every bit as painful as it sounds.

I also realize that the crack in the helmet (which I did not find until the next day) could have been a crack in my head. I'll never ride without a helmet again.

Nathan Taylor

Living in Philadelphia, I consistently bike to work. I never wear a helmet (much to my mother's dismay), and I consistently beat the auto commuters who travel the same route.

I read that bicycles are 95% energy efficient, compared to autos 25-30%. Does anyone know if that figure is accurate?

David Ignatius

Yes, 180-pound bicyclists have a legal right to "share the road" with 3,000-pound SUVs, but that doesn't make it a smart thing to do.


I just started riding my bike to work, a few miles each way through busy downtown Phoenix. Phoenix is not a bike-friendly city. There are very few bike lanes, so I ride on the sidewalk. Illegal, I know, but I'd have to have a death wish to ride on the street.

Motorists here have absolutely no regard for cyclists. I have to be hypervigilant at all times. I always give cars the right-of-way even though it's mine because if I don't, I'd get into accidents. Hasn't happened yet, but you won't catch me without a helmet, because if it happens, I don't want my brains splattered all over the street.

Robert McCoy

I cycled for about 33 years continuously. I had 4 accidents I can recall. None were head injuries. Only in one did I need to be driven to the hospital where they told me just to stay in bed a few days. (Hairline crack in my hip, if you had to ask).

I only wore a helmet for a few of those years. I don't believe in them at all, but I have to admit you are in charge of your own safety. Take the precautions that let you be confident that you'll come home alive. I reccommend that the yellow/orange vests may be the best preventative device you can have; drivers hit what they can't see. Oh, and they can't see bicyclers very well at all.


So far, all the bike accidents I've been in have not involved cars and have been entirely the fault of my inexperience. One time I went over my handlebars, the bridge took a chunk out of my helmet. Sure glad I wore it, though I still passed out (so I guess it didn't slow down my brain enough for it to not smash against my skull).

Helmets are mandatory in Seattle, so it's not as likely to imply any particular level of experience. There are a lot of riders, too, but we just recently had a death similar to what the poster from Portland described.

Dave Atkins

I've only had a couple crashes; neither involved a car. In one I hit a pothole at about 30mph and flipped my bike end over end and cracked my helmet. I always wear a helmet.

I think the danger factor is highly overrated. I bike commute from the suburbs into Boston about 2-3 days a week, 13 miles each way. It is a challenging ride at times, but you learn to be smart and careful.

Marcos Dinnerstein

In re: to post # 6 - MRB from Portland. I think he's on to something when he points out that the consequences for motorists being in car-to-bike accidents are nil. It almost makes me want to bike bedecked in high explosives, primed to detonate on moderate impact. That would certainly be a vivid lesson to the next of kin wouln't it. I did say almost makes me want to. In fact it would muss my hair more thorougly than my helmet and we can't have that can we? In NYC having protected bike lanes is the way to go.


The main reason adult cyclists are at risk of death or serious injury while riding bicycles is that American drivers have an arrogant sense of entitlement--to driving at the speed they want, where they want, when they want, with no impediments besides other cars and the occasional traffic light, which many of them apparently feel free to disregard, too, when it suits them. Almost none of them can be bothered to actually look out for cyclists (or pedestrians). A minority will defer to the cyclist when they do notice. And a small but potentially deadly number of drivers will display their displeasure at having their "right" to the road impinged upon by a cyclist with behavior that should, but never does, result in permanent license revocation.

I've put up with this for twenty years and 100,000+ miles of biking in all conditions and on all types of roads, and have concluded that there are three keys to safety. One, ride confidently and predictably, i.e. assert your right to the road, but ride responsibly so cars know what you're going to do. Two, don't trust anybody, even the ones who act like they're paying attention. And yes, wear a helmet.



# 193 wrote "As an avid cyclist who's been hit a few times, I finally got fed up and began taking my handgun along with me when I ride. This has been most effective! Trust me, motorists give you a wide berth after they spot a .45 strapped to your spandex'd hip. "

Only in the US of A...

Finally a good argument in favour of the right to bear arms - but hold your fire [pun intended] I am in no way inclined to hijack the thread.


There were two whitepapers published in the last two years analyzing helmet use in skiers. As there is substantial record keeping by the National Ski Patrol which records every incident patrollers render assistance in, these studies were very well received, one in the US, the other in Europe. I believe they were referred to as the Sugarbush and Norway whitepapers.

The papers showed that skiers that use helmets are more likely to get head injuries. There is a substantial "perceived invincibility" factor while wearing one and a greater exercise of caution while not wearing one.

One thing to also consider is that helmets actually absorb very little force and the skull is very strong. There's a fair bit of evidence to show that a helmet does nothing against the type of severe impacts that will cause serious head injury. What a helmet does is protect against perhaps mild concussions and soft tissue injuries.

Also consider that helmet industry has a strong stake in promoting their use beyond keeping riders safe. Most helmets cost between $5-$15 to produce, but they retail anywhere from $20-$200. The profit margin is huge.


Robert Harrison

Yes littlewaywelt, I see the British study on cars passing helmeted bicyclists as unconvincing. The data were collected for only one bicyclist, and that bicyclist was the person doing the study. Studies like this are frequently shown to have been biased by the researcher, either consciously or unconsciously. The study would be hard to do well. For instance, even if the researcher had used multiple subjects and hidden from them the purpose of the study, one couldn't, with the equipment used, say whether cars were passing closer to the bikes or the bikes were driving closer to the cars.

I don't dispute that there is a possibility that drivers pass closer to bicyclists, I just don't believe it to be clearly demonstrated. And, as I also pointed out above, only a small percentage of bike-car accidents are related to overtaking (3% is my memory, but it's been a long time since I looked).

And to Jennifer, yes, many bicyclists need to follow the laws more closely (indeed, my memory of bike-car accident statistics is that nearly half are caused by bicyclists who were riding the wrong way or failed to yield right-of-way). However, drivers need to be held to an even higher standard: it is the driver who is in command of the far more dangerous vehicle. Drivers who don't signal when they are supposed to, don't stop when they are supposed, drive faster than they should... - why do these people still have licenses?


Nils Elde

I wiped out riding home from work summer before last, and if not for my helmet I would have definitely had a concussion or at least a trip to the ER. I smashed my head when I landed so hard it broke my helmet and I had to get a new one.


From the standpoint of safety, swimming in the ocean, playing football with friends, or any other athletic activities are "not safe" to a certain extent. There is always a risk of injury.

I do not bike to work due to a long commute but would like to start. I ride about 100 miles per week, a lot or a little depending on your interest in cycling, and I always wear a helmet. So do my riding friends.

Keep in mind, a helmet is not meant to prevent accidents from happening, but meant more for protection to reduce the severity of a head injury in the event of an accident.


I would dearly love to bicycle to work as I only live about 5 miles away. But it would surely get me at least harmed as I have to cross a busy highway with no stop lights to cross at loaded with commuters yapping on cell phones, doing makeup, and eating breakfast.


Bike helmets are completely ineffective until you need one.


Drivers pass closer to bikers wearing helmets because they assume that helmeted cyclists are more experienced. This probably increases your chances of getting hit. I read another study (can't find it) in which the researcher wore either a helmet or not; during the course of the study, he was only hit while wearing his helmet.


I have been hit twice by cars, both times I flew through the air and landed head-first. Seeing the dents in the foam, I was very glad to be wearing a helmet both times.


Here in Portland we just had another bike fatality which caught alot of news attention.

One of the issues is that when it is a 'no-fault' accident (as was likely the case in this instance, in which a 19-year old girl was run over by a cement mixer) not only are there no meaninful fines or penalties, but generally the offending vehicle remains undamaged.

Having your car totaled, your life put in danger, and a hefty penalty are strong disincentives to getting in a car-to-car collision; such a structure isn't in place with bicycles or pedestrians. Perhaps there ought to be?


There was a cyclist in Madison WI that was cut off by a truck turning in front of him he slid under the tire and the truck ran over his head. Busted the helmet but he walked away fine. So as Taleb would point out - it may be a black swan but the risk is so high (getting head run over without a helmet would be "bad" as Egon would say) that we need to be well aware of the payoff vs pure probabilities.
Below is one reference to the story.