http://www.grist.org/article/2010-10-11-theres-safety-in-numbers-for-cyclists
There's safety in numbers for cyclists 9
Default badge avatar for Elly Blue
by Elly Blue
11 Oct 2010 8:04 AM
Illustration Omitted:
People bicycling in
Philadelphia.
During last year's transit strike in Philadelphia, bike ridership
boomed. That likely made streets safer for cyclists.Photo: Kyle
GradingerIn U.S. cities, there are a lot more people out bicycling
than just a few years ago. You might reasonably think that the bicycle
crash rate would skyrocket as more people, from wobbly new riders to
the outright safety-averse, take to the streets on two wheels.
It's a fine, common-sense assumption -- that happens to be wrong.
Research has been steadily showing, actually, that the more people are
out there riding bicycles, the safer bicycling becomes. As ridership
goes up, crash rates stay flat. It's happening in Portland (see page
11 of this report [PDF]). It's happening in New York City.
Much of the ridership increase is due to cities' investments in
bicycle-specific infrastructure. But the efficacy of that
infrastructure for safety is often questioned. And there's one theory
-- based on a growing body of data -- that suggests that a few painted
lines on the road, bike racks, and traffic lights form only part of
the safety equation. And maybe a smaller part than we tend to
assume.
The phenomenon, dubbed "safety in numbers," was first
identified in 2003, in an academic paper by public health researcher
Peter Jacobsen [PDF]. After being asked by officials in Pasadena,
Calif., if their city "was a dangerous place to bicycle,"
Jacobsen began looking at crash data from various communities where
bicycle ridership had fluctuated over time.
What he found surprised him: The number of crashes involving bikes
correlated with the number of riders in a community. As ridership
fluctuated, so did the crash rate. More riders, fewer crashes; fewer
riders, more crashes.
This happened too abruptly, Jacobsen decided, to be caused by
slow-moving factors like infrastructure development and cultural
change. Bicycling becomes safer when the number of riders increases,
he concluded, at least in part because the number of riders
increases.
The inverse happens, as well. One data set Jacobsen looked at covered
49 years of biking history in the United Kingdom. Those numbers showed
that cycling became safer during the oil crisis of the 1970s, caused
by the OPEC oil embargo. Once the crisis ended, both ridership and
safety dropped.
This all must sound terribly wonky. Actually, it's been
revolutionary.
The idea of Safety in Numbers has slowly built up steam in traffic
safety circles since Jacobsen introduced it. Supporting data continues
to quietly (and sometimes dramatically) roll in from around the world,
influencing mainly traffic engineers and planners who are trying to
figure out how to improve bicycle safety.
Bicycle safety is often seen in a sort of vacuum. Helmets tend to
dominate the conversation, with visibility -- lights and bright
clothing -- taking a close second. More sophisticated conversations
get deep into infrastructure: Which is better, sharrows, bike lanes,
or separated cycle tracks? We discuss educating cyclists in defensive
riding techniques and the rules of the road.
These are all good and important efforts. The problem is what's
missing. Here's the core of Jacobsen's analysis, from the 2003
"Safety in Numbers" report:
Whose behavior changes, the motorist's or that of
the people walking and bicycling? It seems unlikely that people
walking or bicycling obey traffic laws more or defer to motorists more
in societies or time periods with greater walking and bicycling.
Indeed it seems less likely. ... Adaptation in motorist behavior seems
more plausible.
So why might this be the case?
When there is a serious bicycle crash, it almost always involves
someone driving a car. There are any number of ways drivers become
involved in these crashes, primarily involving speed, turning, and the
myriad distractions that are common behind the wheel.
But when there are a lot of bicyclists on the road, according to this
theory, drivers take notice. They become more attentive, slow down,
pass more cautiously, double-check their blind spots, expect the
unexpected. They sense that the road has become a more complicated
place, and adjust their behavior accordingly. As a result, the road
becomes safer, presumably for everyone.
Safety in numbers is an important idea that has shifted the way
planners and engineers think about bicycle safety. But it won't be the
final word. We will doubtless see this idea bandied back and forth for
some time, especially as academic interest in bicycling and walking
increases. As data improves we'll likely see a more complex
relationship emerge among ridership, safety, infrastructure, laws, and
culture.
Whatever the variables, as Jacobsen told me in a requisitely wonky
email, "The bigger SIN story is that those cities /countries that
have encouraged bicycling have been rewarded with more trips by bike,
and not just a non-linear increase in injuries, but a decrease in
injuries."
That's huge. Safety in numbers will prove over time, I suspect, to be
the first major theory based on objective data that can break down the
double standard we all pedal under. Jacobsen's research calls into
question the foundation of a system in which the convenience of
driving is exalted above the basic safety and mobility of people
walking and bicycling.
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