Last week there was a tragic and fatal bike accident here in Halifax. As avid road cyclists, these sorts of accidents always hit home for my wife and I. Even moreso in this case, as the cyclist’s description (an elementary-school teacher and cycling enthusiast in her early 30’s) is also an apt description for my wife.
Although the cause of the crash is still unclear (the cyclist was hit by a truck turning right, although no word yet on whether anyone was at fault), these sorts of accidents drive home the fact that riding a bike can, at times, be a dangerous activity. And so, I thought this would be a good time to revisit just how dangerous cycling is, when compared to other modes of transportation.
The most useful information that I’ve encountered on this topic is from a 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! There is a reason why you don’t hear about out-of-control cyclists taking out a swath of pedestrians. 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!
Lest that you think that this is only true in the cycling utopia that is the Netherlands, similar studies have also suggested that the benefits of cycling outweigh the dangers in countries ranging from Spain to India and the UK. Just this week it was reported that after 8.75 million trips covering more than 14 million miles, there has yet to be a single fatality associated with the new Citi bike-share program in New York City (there have been only 100 reported accidents so far, and only 25 of those warranted a trip to the emergency room). When you consider that the people most likely to use a bike-share program are tourists and other individuals who don’t spend a lot of time on a bike, those results are very heartening. Especially when you take into account the many failings of urban cycling in North America (see videos below).
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. It is interesting and extremely important to note that the number of cyclists on the road is inversely related to the number of car/bike collisions – 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 some cycling related deaths.
Today’s post is an update from a post published on Obesity Panacea in September of 2010.