Do the health benefits of cycling outweigh the safety risks?

A recent spate of cycling accidents in Montreal and Winnipeg begs the question
Photo by helter-skelter/Flickr

The Statement:  “To be sure, cycling provides good exercise, but there are safer ways to get it. […] Second, bike riding here is not as environmentally virtuous as it’s cracked up to be.”—Montreal Gazette, 08/11/2011

This Gazette story was prompted by a series of five very sad cycling fatalities in Montreal this year, “an unusually high death toll,” the writer lamented, before going on to list myriad downsides related to cycling in the urban environment. The Winnipeg Free Press published a similarly disturbing article, which noted that in the last 18 months, 29 people have died on Winnipeg streets in car crashes, and 18 of them were pedestrians or cyclists. The Winnipeg Free Press article’s message was as clear and pedantic as its title: “Walking, cycling can be deadly.”

Ontario doctors have likewise called for safer cycling. They note that while biking is good exercise, the government needs to invest in cycling infrastructure, such as purpose-built bike lanes, to make commuting on two wheels safer. The provincial NDP in Ontario offered another (seemingly unlikely and impossible to enforce) solution to the problem of cars and bikes mingling dangerously on the road: they suggested changing the Highway Traffic Act so motorists can be fined for crossing a one-metre buffer with cyclists.

But what is the evidence behind these proposed cycling policies? And if cycling is as dangerous as these news articles purport, do the health benefits of cycling outweigh the risks? Or should people refrain from biking on city streets altogether?

I looked at a myth-busting evidence review produced for the Canadian National Collaborating Centre for Environmental Health. First, the good news: people who choose “active transport” (walking and cycling to get around) are, on average, more fit and less overweight and obese than motor-vehicle users. As well, all-cause mortality, disease-specific mortality, and cardiovascular risk are lower in this group. Exercise for transportation is also found to be sustained more consistently throughout a person’s life than other workouts, such as gym regimes.

Now, the bad news: people who choose active transport face higher risks of fatality or injury per distance travelled than people who use cars, buses, or rail, according to the review. A 2003 study published in the American Journal of Public Health found that the fatality risks per distance travelled for U.S. pedestrians and cyclists are 23 and 12 times higher, respectively, than for drivers. A study that looked at injury rates for Norwegian pedestrians and cyclists per distance travelled found they were 4 and 7.5 times higher, respectively, than for those who travelled by car.

There is no Canadian data on the absolute risk of injury and fatality for cyclists, but there are a few things we know about how bike accidents happen here. Transport Canada, which tracks crashes between cyclists and road motor vehicles, reported that 64 per cent of these deaths occurred on urban roads, and the peak time for crashes was afternoons and evenings. Bicyclists also make up the smallest percentage of road fatalities compared to other road users. For example, people who died while biking in 2009 made up 1.9 per cent of fatalities on the road (compared to 53.1 per cent for drivers, 19.5 per cent for passengers, and 13.9 per cent for pedestrians).

Of the risk to Canadians, Kay Teschke, a professor of public health at the University of British Columbia who studies cycling in cities, told Science-ish, “The fatality rates are about the same for cyclists and pedestrians, though the numbers of pedestrians killed is much higher, because more people walk. Of course, the numbers of motor-vehicle fatalities is much higher than either cycling or walking.” She concluded: “The safest mode of transport by far is transit—like buses or subways —there’s no question about it.”

So what would make cyclists safer: bike lanes or a one-metre buffer? Teschke noted that the evidence shows purpose-built bike lanes seem to be the way to go. “One of the interesting features that has been found in North American cities where European-style separated bike lanes are being installed is that this is not only lowering cyclist crashes, but also pedestrian and motor vehicle crashes.” She also pointed to European centres where bike-specific infrastructure is ubiquitous and cycling injury rates are much lower than in the United States. (See this comparison of American, Dutch, and German cyclists, which shows Americans are twice as likely to get killed as Germans and over 3 times as likely as the Dutch per kilometer and per trip cycled.)

Other studies from Europe indicate there are large net benefits of cycling. A 2010 review in Environmental Health Perspectives looked at cycling in the Netherlands—with its extensive cycling networks—and found that, “on average, the estimated health benefits of cycling were substantially larger than the risks relative to car driving.” A recent review published in the British Medical Journal, which looked at the risks and benefits to health of travel by bicycle, came to similarly positive conclusions. “The health benefits of physical activity from cycling using the bicycle sharing scheme (Bicing) in Barcleona, Spain, were large compared with the risks from inhalation of air pollutants and road traffic accidents.” One of the study authors told Science-ish, “Our findings are applicable to other cities, although the risk benefit ratio may change depending on the level of pollution between cities, as well as the risk of traffic accident. But the benefit of physical activity will remain constant.”

So, here in Canada, to cycle or not to cycle? Teschke said, “I think getting exercise is a major problem in North America, and though we have higher [injury and fatality] risks from cycling than in Europe, we have higher risks from obesity, as well. So, in North America, while the risks are greater, the benefits are greater as well.”

It’s important to note, too, that there is a well-documented “safety in numbers” effect for pedestrians and cyclists, meaning that as more people get on their bikes or walk to work in a city, the safer these methods of transport become. “In the Netherlands, which has some of the highest cycling rates in the world (almost 30% of all trips are by bicycle) the injury risk for cyclists is 1.1 cyclists injured per 10 million km cycled. In comparison, in the UK and the U.S. only about 1% of trips are made by bicycle, and the risk is 3.6 and 37.5 cyclists injured per 10 million km cycled,” the 2010 evidence review stated.

Teschke is hopeful that as more awareness is raised in Canada about the benefits of cycling and the need for biking infrastructure, the roads will be safer places for motorists on two wheels.

In fact, already, the number of fatalities for cyclists has been decreasing. In 2010, Transport Canada reported that “bicyclists accounted for about 2 per cent of traffic fatalities, with an average of 60 bicyclists being killed each year in collisions with motor vehicles.” This was a 2 per cent decrease from the 1996-2001 period. Similarly, this summer, the Canadian Institute for Health Information put out a press release that said while “the annual number of cycling injury hospitalizations remained relatively stable between 2001–2002 and 2009–2010, the number of cycling-related head injuries decreased significantly, from 907 to 665, over the same period.”

By now you may be wondering: what about that ubiquitous bicycle appendage, the helmet. Is it safer to wear one? Stephen Walter, a professor in clinical epidemiology and biostatistics at McMaster University, told Science-ish, “Some people argue they increase risk because their use may encourage riskier behaviour by riders and drivers.” But he added: “Conditional on being in an accident, I know I would rather be wearing one than not. If you’re going to bike, wear a helmet.”

Science-ish is a joint project of Maclean’s, The Medical Post, and the McMaster Health Forum. Julia Belluz is the associate editor at The Medical Post. Got a tip? Seen something that’s Science-ish? Message her at [email protected] or on Twitter @juliaoftoronto