Do the Health Benefits of Cycling Outweigh the Risks?

Image by Wolfgang Staudt

Regular readers of Obesity Panacea will know that I am a huge fan of active transportation, which entails commuting via active means (e.g. walking, cycling, or taking public transit) rather than driving.  But when I talk with my friends about the many health and societal benefits of active commuting by bicycle, they almost always bring up the fact that they value their lives too much to risk cycling on busy city streets.  This is obviously not a trivial concern – here in Ottawa there were three cycling deaths in a three day period in August, and another tragic death occurred earlier this week (although in at least 2 of those accidents, it may have been cyclist errors which resulted in the accidents).

So I was extremely interested when I came across a recent paper in Environmental Health Perspectives which examines whether the benefits of increased cycling (increased physical activity) outweigh the risks (both in terms of accidents and exposure to pollutants for individual cyclists).   To calculate these numbers, the authors examine changes in mortality at both the population level, and for individual cyclists, if 12.5% of current short car trips in the Netherlands were to be performed by cycling instead.

So, what did they find?

The authors report that for most adults, the risk of death when cycling is about 4.3x higher than if the same trip were being made by car (YIKES!). However, we’ve got to remember that commuters not only pose a risk to themselves – they also post a risk to other road users.  And if you’re going to be hit by a vehicle, a Cervelo is going to do you a lot less harm than a Corolla!  So with an increase in the number of trips made by bike, the increased mortality among cyclists due to traffic accidents is offset by the reduced mortality among the general population who would be less likely to be run over crossing the street (interestingly, if it were high risk young drivers who were to switch from driving to cycling, it would actually save lives!).

Now while the risk of being in an accident is higher for cyclists, it must be remembered that they are also likely to be getting increased levels of health promoting physical activity, and substantially reducing their volume of sedentary time.  In fact, the risk of death due to physical inactivity among active commuters is estimated to be 10-50% lower than in non-active commuters – a pretty substantial health benefit!

So will cycling to work make your life longer or shorter?  On average, the risk due to car accidents will reduce your life expectancy by just 5-9 days.   Being exposed to air pollution during your commute could cost you another 8-40 days.  But the physical activity in your commute would actually increase your life expectancy by up to 14 months! Overall, the health benefits of active commuting by bike are 9 times greater than the risks!

What’s the take-home message?

Cycling is obviously more dangerous that it should be, something which needs desperately to be addressed.  But if you decide to commute by bicycle on a regular basis, you are far more likely to improve your health and prolong your life via increased physical activity than you are to shorten your life by getting involved in an accident.  Interestingly, the number of cyclists on the road is inversely related to the number of cycling deaths – so the more of us that get out on the roads, the less likely we are to get in an accident.

And if you do choose to cycle more regularly (which I definitely think you should!), please wear a helmet and obey traffic laws – especially stop signs.  Those two factors alone will go a long way to preventing cycling related deaths.

Travis

ResearchBlogging.orgJohan de Hartog J, Boogaard H, Nijland H, & Hoek G (2010). Do the health benefits of cycling outweigh the risks? Environmental health perspectives, 118 (8), 1109-16 PMID: 20587380

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26 Responses to Do the Health Benefits of Cycling Outweigh the Risks?

  1. Hilary PhD says:

    You say “although in at least 2 of those accidents, it may have been cyclist errors which resulted in the accidents” as if that somehow means they don’t count. The main reason I don’t cycle is because I know I am a poor cyclist, liable to make mistakes. I used to cycle when I lived in a very cycle-friendly city where drivers were more aware (and got by with nothing more than a few scares and near misses), but I know I could not do so safely where I now live. I suspect that many people who say cycling is “too dangerous” mean, as I do, that it is too dangerous for them based on an assessment of their personal risk and lack of skill. The data can only reflect the risks among people who do cycle, not what the risks would be if non-cyclists cycled.

    Also, you don’t mention non-fatal injury. My impression is that is a fairly major risk that needs to be taken into the equation.

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    • Travis Saunders, MSc, CEP says:

      Both good points Hilary. I wouldn’t go so far as to say that cyclist-error means that the accidents somehow “don’t count”, but I do think it provides some necessary context. Perhaps cyclist “error” wasn’t even the proper term for me to use – in one case I was referring to it appears the cyclist may have been drunk and riding at night without a helmet, and in the other case the cyclist ran a stop sign. To me personally, hearing that a cyclist was run over in a bike lane (which has also happened in Ottawa) inspires much more fear than hearing that someone was behaving in an obviously dangerous fashion.

      I have had several friends say that they would ride to work if there were sequestered bike paths for the entire trip, which echoes your statement about some environments being more bike friendly than others. To me that suggests that we need to do a better job of making environments safe for cycling, but I still think that the benefits, for most people, will outweigh the risks of having an accident. Keep in mind as well that depending on where people live, some trips may be perceived as being much more bike friendly than others, and public transit in most cities will also accommodate bikes, which can allow people to bypass the more dangerous parts of their cycling trip. It’s not about always commuting by bike, but doing so when possible, and hopefully increasing the bikeability of all neighbourhoods over time.

      Good catch on the non-mention of non-fatal injury – those estimates would be far more difficult to make (since non-fatal injuries are not reported as effectively as fatal injuries), so the paper focused exclusively on fatal injuries. I would love to see a similar paper focusing on non-fatal injuries, but given the logistical difficulties I think it could be a long ways down the road.

      Travis

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  2. Ruth Seeley says:

    Can you point me to any stats on use of helmets reducing death? I ask because my local city council in Lethbridge is currently revising its bicycling by-law – the draft legislation is flawed, but I’m concerned that some of the opposition to the by-law focuses on the requirement for adults (not just children under age 18) to wear helmets. If you can point me to something recent on the subject of helmets reducing head injuries/cycling deaths without too much trouble, I’d be eternally grateful.

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    • Travis Saunders, MSc, CEP says:

      Nice to hear from someone in Lethbridge! I raced in the Moonlight Run most years during my undergrad at U of C, that coulee is awfully steep!

      Here are a number of resources which I think you’ll find useful:

      Here is a sprawling site with a number of stats, including the % deaths among cyclists broken down by helmet usage (~90% of deaths occur in those who don’t wear helmets, and about 1/4 have blood alcohol levels above the legal limit for operating a car): http://www.helmets.org/stats.htm

      Here are the details on the substantial reductions in deaths once helmet use was mandated in Victoria, Australia – http://www.cdc.gov/mmwr/preview/mmwrhtml/00020531.htm

      Here is a Cochrane Review on the impact of helmet legislation itself:
      http://www2.cochrane.org/reviews/en/ab005401.html

      And finally a study in Ontario that also suggests that helmet laws play a role in reducing mortality: http://pediatrics.aappublications.org/cgi/content/abstract/122/3/605

      Good luck with the helmet laws in Lethbridge! Let me know if you have any trouble accessing the data or papers,

      Travis

      Travis

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    • Charles A-M says:

      (I’m a former President of Citizens for Safe Cycling, which promotes cycling as a mode of transportation in Ottawa. I wear a helmet while cycling, and I oppose mandatory helmet legislation.)

      Great article, Travis.

      Ruth, There are lots of studies saying lots of things, and they’re often based on difficult-to-verify evidence due to so many extraneous variables. In Ontario, for example, there is fairly poor enforcement of the law that requires children to wear helmets. There are a number of directions you can go from this point (is increase/reduction in injury therefore attributable to the law?).

      Some studies suggest that rates of cycling decrease with mandatory helmet laws. Coupled with the well-recognized relationship whereby collisions go down when there are more cyclists, one could interpret that a mandatory helmet legislation can increase danger if it reduces incidence of cycling.

      Maybe people who wear helmets are more likely to ride safely, and thus less likely to get into a collision (I’ve had a few near-misses where my quick wits and defensive riding have saved me from getting hit)–if this is the case, the statistics would then appear to say that helmet use reduces collisions.

      A helmet will also only help if it’s worn correctly. If the straps are too loose, it’s too far back on the head, it’s too old, or if you’re wearing a baseball cap underneath, the helmet may not reduce injury (and in some cases, may even increase it). Beyond a certain speed, a helmet will not do enough to save your life, so when news reports say that a struck cyclist was/wasn’t wearing a helmet, that doesn’t necessarily mean the outcome would have been different if the helmet variable were different.

      Cycling safety is a public health issue, and the threat of police interaction shouldn’t be the first and only way to encourage safe riding techniques. If you really want to promote safety, you don’t just threaten people with fines to get them to wear helmets, you also teach them why it’s important to wear a helmet, and teach them how to do it safely. You don’t need mandatory legislation to have these public education campaigns.

      But most importantly, we have to break the myth that helmet use is a panacea for cycling safety. A helmet only helps you once you’ve gotten in a collision. To reduce your chances of getting into a collision, take a defensive cycling course (such as the CAN-BIKE courses available in many parts of the country), lobby for your local police to enforce laws against dangerous behaviours by motorists (and cyclists), and lobby for your municipality and province to improve road infrastructure for cyclists.

      Vélo Québec is one of the largest and most successful cycling groups in North America, and they have lots of experience. The City of Ottawa has brought in a couple of their members to consult on a segregated bike lane pilot project here in Ottawa. Perhaps Lethbridge would be well served by inviting cycling experts from out of town to help re-draft the legislation…

      Looking at the press release announcing Lethbridge’s legislation, a lot of what that by-law proposes wouldn’t be within the jurisdiction of a municipality in Ontario, but I guess that’s why we have different provinces.

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      • Travis Saunders, MSc, CEP says:

        Wow, thanks for that fantastic response Charles! Much appreciated.

        Travis

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  3. Ruth Seeley says:

    Thank you SO much. When I said the legislation was flawed, part of the problem is that it attempted to lump all non-automotive wheeled traffic into a single by-law (including motorized wheelchairs and skateboards!) as well as proposing to allow cyclists to ride on the sidewalks in the downtown core – which in my view is wrong, because it doesn’t acknowledge a cyclist’s right to be on the road (and obligation to follow the rules of the road). It’s going to be redrafted, but I really appreciate your fantastically speedy response and all the info you’ve provided. Lazy of me to just ask you, but on the other hand, why reinvent the wheel?

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    • Travis Saunders, MSc, CEP says:

      Glad I could help! Personally I think cyclists should be on the road, but with a bike lane. Putting them on sidewalks is dangerous for all kinds of reasons (and really annoying for cyclists), but having a bike lane makes people more comfortable and increases the chances that non-cyclists will use the roads.

      Keep me posted on how it works out!

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  4. Erika M says:

    I’d be curious to see that study repeated here in the U.S., because I’m guessing the risks here are significantly greater than in the Netherlands. Our vehicles are bigger and hog more of the lanes, we rarely have bike lanes or sidewalks, and the culture here is much less accepting of bicyclists. I used to cycle quite a bit in the last town I lived, and got used to drivers rolling down their windows and shouting rude remarks (“get off the ****ing road”) as they sped past. And that town was positively bicycle-friendly in comparison with where I live now. My current city is designed with motorists in mind — no real bike lanes, no sidewalks, and lots of roundabouts instead of four-way stops (merging onto a roundabout on a bicycle is not a happy experience). Our mayor recently started a push to encourage people to cycle more, and painted bike lanes downtown… except that the “bike lanes” consist of painting a yellow line on the edge of already narrow city streets. So as a cyclist you’re hugging the curb next to irritated drivers whose cars barely fit into the narrowed lane.

    What I would LOVE to see more of is the rails-to-trails initiative, where unused railroad tracks are converted to sheltered bike paths. I used to live near a network of paths and cycled 100+ miles a week. Now I live in the city and my bike sits in the garage.

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  5. Chris says:

    I just took my bike out on the weekend for the first time in a long time and had trouble enjoying the ride. Even on a bike path you still have cars turning in and out and then you have to hop on and off at intersections etc. I think the main way I could relax and enjoy riding as a beginner would be to stick to park trails.

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  6. Erin says:

    I have never understood the legislation that bikes should not be on sidewalks, but should be on the road regardless of the hazard it creates with cars swerving into the other lane to avoid you. That legislation would make more sense if bike lanes were everywhere.

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    • julie says:

      As a cyclist and a auto driver, I find biking on the sidewalk to be incredibly dangerous, especially for the cyclist. Cars are not expecting a fast moving vehicle to be popping out, instead of a slow-moving pedestrian. This is not to say that there are plenty of sketchy streets where I take the sidewalk instead of putting myself in the lane of traffic (and I TAKE THE LANE-cars can move over to pass me-I value my life more than their convenience), but if I do take the sidewalk, I don’t expect that anyone will expect me in the intersection, so I wait.

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      • julie says:

        BTW, my city has plenty of signage about how cyclists should take the lane, and bike lanes, but there are still a*holes who want to argue about it, regardless.

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        • Travis Saunders, MSc, CEP says:

          Just to add to your point Julie – the one time that I was ever involved in a bike accident, was when I was cycling on the sidewalk in undergrad. A car came out of an alley and onto the sidewalk without stopping. I would probably have been hit if I had been running instead of cycling, but it was the last time I rode my bike on the sidewalk when not absolutely necessary.

          Travis

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  8. Maryn says:

    I echo Hilary’s points. I’m an anxious and inept biker around cars despite living in Minneapolis, reputedly one of the most bike-friendly cities in the US. (I didn’t learn to ride a bike til well into adulthood and so never benefitted from general childhood fearlessness.) I’m about to move to a significantly less bike-friendly city and anticipate that I’ll have to bike less than I do now because the streets are so bike-unfriendly. It makes me sad because I support biking in general and would like to do it, but the mix of narrow streets, hostile drivers and nervous biker is not a good one.

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    • Travis Saunders, MSc, CEP says:

      Maryn and Hilary, what are the types of things that would make either of you comfortable cycling regularly? Bike lanes on streets, totally sequestered bike lanes, less vehicle traffic, etc? I admit that I have a pretty high tolerance for traffic (my girlfriend is even better – she bikes throughout Canadian winters while barely batting an eye), so I’m wondering what changes are necessary for less adventurous cyclists to take to the roads more often.

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      • Hilary PhD says:

        Totally sequestered bike lanes, conceivably.

        Realistically, here in London, I think the streets are too narrow and the traffic too heavy for it to be feasible to design bike lanes that would ever make me comfortable about cycling. I don’t contribute to that traffic as I don’t drive either, I combine walking with public transport. Actually, our excellent buses are part of the problem – they are wide and really squeeze the bikes badly on the shared lanes.

        It’s easy to say, as one commenter does “to reduce your chances of getting into a collision, take a defensive cycling course” but frankly a) that’s a big time investment on top of the big cash investment in buying a bike and b) I used to cycle regularly, I had police training as a child, I know what I’m supposed to do, and it still doesn’t make me any safer because I don’t control the bike well enough to do basic things like taking a good look over my shoulder or giving clear hand signals without wobbling dangerously.

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  9. Faith says:

    I’ve lived in Victoria, Australia since those compulsory helmet laws were introduced and the story is not as straightforward as that painted in the document linked to above.

    There was a significant drop in cyclist fatalities and head injuries but at this time there was a similar drop in the same amongst pedestrians and car passengers. At the same time that helmet laws were introduced big campaigns against dr ink driving and speeding were also started. These had a huge impact on injuries and fatalities across the board.

    Cycling colume dropped by an even greater volume tah the decrease in acidents. Less cyclists on the road means less accidents involving cyclists. Unfortunately what it also meant was a more dangerous environment for those who continued to ride. The single most significant factor in creating a safe cycling environment is the volume of cyclists on the road. Significantly, it was largely women and children who stopped cycling. The perception that cycling was no longer an everyday activity but a dangerous one meant that the majority of cyclists tended to be young, risk-taking males who ride with an aggressive attitude. These are the same group who have the greatest chance of being involved in an accident when they are driving a car. It has also lead to a spiraling antagonism between motorists and cyclists.

    Introducing compulsory helmet laws in Victoria has only led to a more dangerous cycling environment. We have thousands of ams of bicycle paths, on road and off, but it is not until we se more ‘everyday’ cyclists, rather than Lycra clad road warriors, that we can create a safer environment by affecting driver behaviour

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  10. Travis says:

    Thanks for that, Faith.

    My girlfriend and I have debated compulsory helmet laws a few times – like Chris, she wears a helmet but is concerned about the issues you mentioned in Victoria. Personally, I lean more towards a compulsory helmet law, but you and Chris bring up some good points.

    Travis

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  11. ABradford says:

    Nice to see a post on this research. The comments here definitely bring up some interesting cultural considerations in the safety of conversion to more active transportation. As an example, I was brought up in a suburb with little in the way of bike lanes and very few cyclists. I remember frequently available bike safety training with the local police department there, even for adults. This is incredibly different from the campus that I now work on and commute around on bike. Here, there is a huge population of people on bikes and reasonably good bike lanes, but little awareness of bike safety and courtesy. I think both places are vastly different in how to approach safety with bicycles (such as helmet laws) while still encouraging active transport.

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  12. Stephanie says:

    Hey Travis,

    In preparing a lecture looking at bicycle safety from the built environment perpective I cam across this abstract:

    Interestingly, the authors conclude that biking results in more injury than the same trips via. motor vehicle…and the research was done in Ottawa no less!

    Aultman-Hall L, Hall FL. Ottawa-Carleton commuter cyclist on- and off-road incident rates. Accid Anal Prev. 1998 Jan;30(1):29-43.
    http://www.ncbi.nlm.nih.gov/pubmed/9542542

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    • Travis says:

      Thanks for pointing that out, Stephanie. I think the findings agree with the paper I discussed in the post – for a given trip, you’re at a higher risk of injury if you’re cycling than if you’re driving. It’s just that this small increased risk associated with cycling injuries is dwarfed by the reduced risk of things like CVD as a result of the increased physical activity. It’s interesting that they note that biking on the sidewalk is the most dangerous place to ride, with riding on the road being the least dangerous! It’s not shocking, but still quite interesting… might be good fodder for a future post! Although of course this is self-report, and you know how I feel about self-report data :)

      Good luck with the lecture, let me know how it goes!

      Travis

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  14. Ash Routen says:

    Good post Travis,

    As a keen cyclist I’m biased towards extolling the virtues of cycling. I definitely think helmets should be mandatory on the road, and also think more consideration from car drivers is necessary (unlike mainland Europe, UK drivers are not so tolerant). I basically ride as aggressively as possible in traffic and give as good as I get, this includes giving the rear of their car a nice dent by kicking it if a driver happens to cut me up and then get caught in traffic! Many people pull out and seem to think that as I’m on a bike I must be virtually stationary, when on the flat I’m going ~25 mph or downhill 25-50mph so I just stick out a bit and let the car drivers wait- not that I’m bitter from past hostile drivers! Definitely keep cyclists off the sidewalk (recipe for disaster), in cycle lanes if possible, offer training for cycling in traffic, and teach cyclists to stick up for themselves!

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