Numbers, not bike lanes or trails, = safety

By Dan Gaffney
September 3, 2008

It seems paradoxical but the more people ride bicycles on our city streets, the less likely they are to be injured in traffic accidents, say injury experts who will speak at a forthcoming cycling safety seminar in Sydney.

Local and international research reveals that as cycling participation increases, a cyclist is far less likely to collide with a motor vehicle or suffer injury and death – and what’s true for cyclists is also true for pedestrians. And it’s not simply because there are fewer cars on the roads, but because motorists seem to change their behaviour and drive more safely when they see more cyclists and pedestrians around.

Studies in many countries have shown consistently that the number of motorists colliding with walkers or cyclists doesn’t increase equally with the number of people walking or bicycling. For example, a community that doubles its cycling numbers can expect a one-third drop in the per-cyclist frequency of a crash with a motor vehicle.

“It’s a virtuous cycle,” says Dr Julie Hatfield, an injury expert from UNSW who address the seminar on September 5. “The likelihood that an individual cyclist will be struck by a motorist falls with increasing rate of bicycling in a community. And the safer cycling is perceived to be, the more people are prepared to cycle.”

Experts say the effect is independent of improvements in cycling-friendly laws such as lower speed limits and better infrastructure, such as bike paths. Research has revealed the safety-in-numbers impact for cyclists in Australia, Denmark, the Netherlands, 14 European countries and 68 Californian cities.

“It’s a positive effect but some people are surprised that injury rates don’t go up at the same rate of increases in cycling,” says Sydney University’s Dr Chris Rissel, who will give the seminar’s keynote address. “It appears that motorists adjust their behaviour in the presence of increasing numbers of people bicycling because they expect or experience more people cycling. Also, rising cycling rates mean motorists are more likely to be cyclists, and therefore be more conscious of, and sympathetic towards, cyclists.”

Dr Rissel says transport authorities should highlight the fun, convenience and health and environmental benefits of cycling, rather than what he views as an undue emphasis on danger and safety messages, which can deter cyclists: “We should create a cycling friendly environment and accentuate cycling’s positives rather than stress negatives with ‘safety campaigns’ that focus on cyclists without addressing drivers and road conditions. Reminding people of injury rates and risks, to wear helmets and reflective visible clothes has the unintended effect of reinforcing fears of cycling which discourages people from cycling.”

Safety concerns are among the most significant barriers preventing Australians from cycling, including among those who cycle regularly, according to a 2008 Commonwealth Government report, Cycling: Getting Australia Moving. Despite this, over 1.68 million adults cycled in 2006, an increase of almost 250,000 since 2001. During this period, Australian capital cities experienced an average 22 percent increase in bicycle journeys to work. Melbourne led with a 42 percent increase, while Sydney lagged the field with a nine percent increase. 2006 figures reveal that 12,132 Sydneysiders cycle to work.

7 replies
  1. Keri
    Keri says:

    This article is definitely an improvement over Jacobsen (whose conclusions I found offensive).

    I think it’s useful to note that shared space road design creates this effect of inducing caution, while placing stripes on the road does exactly the opposite.

    Also, as I often say, when we create the conditions (physical and cultural) that enhance pedestrian safety, bicyclists will benefit from the increased attentiveness of motorists.

  2. Keri
    Keri says:

    John Schubert has written an excellent comment about this on Scientific American:

    “Safety in numbers,” the way it’s put forth, is junk science. A quick look at most accident causes shows this. Most accident causes involve clueless riding, and simply increasing clueless riding increases accidents.

    So why do the numbers show increased safety?

    First of all, the math underlying the “safety in numbers” assertion is suspect. The assertion comes from Jacobsen’s paper, which uses a bunch of equations to make the point. But the equations in the paper don’t prove anything. One researcher plugged random numbers from the phone book into those equations and got a graph displaying results similar to Jacobsen’s results. The equations give the desired result, no matter what data you plug into them.

    Second, increased numbers reflect increased experience among riders, and more cautious riders entering the ranks of cyclists. Thus, you may see better statistics, but the “safety in numbers” effect is NOT making any one individual cyclist safer.

    Why is this an issue? Because “safety in numbers” is used to justify the installation of some really dangerous bicycle facilities, such as some of the bikelanes that have led to fatal accidents in Portland, Seattle, Cambridge and Amsterdam. The proponents of those bikelanes dodge the questions about specific accident causes with the questionable assertion that the facilities draw more cyclists, and that more cyclists will automatically make the accident rate go down. This is sloppy thinking!

    Those of us who are annoyed by the “safety in numbers” junk science are certainly not opposed to more bicyclists. We’re only opposed to junk science being used as an excuse to build unsafe facilities with demonstrated accident causes built-in. The level of safety engineering in bicycle facility design is often quite poor, and “safety in numbers” is used to make it even more so.

    —John Schubert
    Coopersburg, Pennsylvania

  3. Eric
    Eric says:

    I would be a lot happier with Mr. Schubert’s comment (and I suspect so would others) if he had at least an undergraduate degree in statistics.

    I don’t have one, but I have met many people who have degrees in business, education or one of the social sciences who think they are statistics experts because they once took a class in regression analysis. In most cases, their opinion of themselves rapidly deflates when someone who really does know something complains about the way they derived epsilon, or somesuch.

    It’s a shame that Mr. Scubert didn’t give links to the documents he condemns and praises. Jacobsen’s paper
    http://www.tsc.berkeley.edu/newsletter/Spring04/JacobsenPaper.pdf
    was published in a peer reviewed journal. It has been widely cited in all sorts of other journals
    ( http://injuryprevention.bmj.com/cgi/content/abstract/9/3/205 )
    and was the most popular article on this journal’s website two years after it was published.
    http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1730247&blobtype=pdf

    Against this, we have the “one researcher” that plugged random numbers from the phone book into those equations.
    You can read about it here:
    http://www.johnforester.com/Articles/Social/Numbers%20vs%20Safety.htm

    I have been unable to find on the web any other serious criticism of the study. Nor have I read any criticism of the criticism. I would have hoped that someone without an ax to grind and some sort of degree in statistics would have evaluated the study, but alas, that was not to be.

    Mr. Schubert is certainly correct about one thing and that is that the study is being used to press for more bike lanes. However, I don’t think that is the fault of the study. Read it. Jacobsen doesn’t advocate for much except more study.

    The people that press for bike lanes use the argument that “new riders feel safer” in a bike lane. My observations have found that not to be true. In fact, when given an option of the street, a lane or a sidewalk, on the same street, MOST cyclists opt for the sidewalk. Watch the helicopter parents cycling with their children home on Lakemont one afternoon after school to see what I mean.

    Winter Park installed a new traffic light that stops traffic in all directions when the pedestrian button is pressed. They made the light that way because the parents in the neighborhood said the intersection was too dangerous, even with a crossing guard, to have their children walk to school and that if the intersection was made safer, they would send their children to school on foot.

    Three years later, result is not one more child walks or rides across the new and improved intersection than did before. When asked why not, the parents now say that a stranger could jump out of the bushes and kill the kid.

    As Keri said in a post, Whack-A-Mole.

  4. Keri
    Keri says:

    “I have been unable to find on the web any other serious criticism of the study. Nor have I read any criticism of the criticism.”

    That’s because it is just accepted as “common sense.” And that’s why it’s futile to debunk the math. It doesn’t matter if the math is correct or not. Arguing over that is a total distraction. What matters is that the conclusions are used for end-justifies-means rationalization of bad facilities by ideologues (like Pucher, Lusk, Geller) and private-sector firms (like Alta) who make a living exploiting people’s fears to sell this garbage.

  5. pmsummer
    pmsummer says:

    Mr. Schubert may not be a degreed statistician, but he does have a background in investigative journalism, and employs his skills well here.

    We live in a society that treats professions much like primitive cultures treat shamans and witch doctors. We stand in awe of their mighty powers. All too often we don’t ask how, or why… we just take what they say for granted, even though predetermined result-based research has been the dominate “consumer-driven” research paradigm for at least three decades now.

    Don’t forget, in the 1950s and ’60s, US tobacco companies released research that “proved” that tobacco use didn’t cause cancer.

    Cough, cough.

  6. Keri
    Keri says:

    “predetermined result-based research …”

    This is the lens through which we need to view nearly all studies related to bicycling. If you read Wayne’s critiques of bicycle studies, you’ll see this theme again and again.

    Even when the data shows a decrease in benefit to the bicyclists, researchers use bogus surveys and discover that the bicyclists didn’t notice the decrease. Example: the Red Shoulder study in Tavares, FL … substandard 3ft shoulders added to 9ft lanes resulted in motorists passing closer. Surveyed bicyclists thought the opposite. Study conclusion: crappy, substandard facility is good because unobservant bicyclists don’t know any better! Woohoo!

    What that study proves best is that bicyclists are easily placated by the illusion of separation.

  7. pmsummer
    pmsummer says:

    There’s a Traffic Engineering firm in My Fair City that is run by a former director of our Department of Transportation. Many of the traffic impact studies and analysis that developers are required to provide to our Public Works Department and Zoning/Land Use boards come from this firm. Because their studies ALWAYS show what the developer wants (as opposed to helping the developer design to minimize impact), and seldom reflects the reality of the impact, the standard joke here is about the red light hanging outside their offices… and we don’t mean a stop light.

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