Phys Ed: Do More Bicyclists Lead to More Injuries

Great article by Gretchen Reynolds in yesterday's NY Times Blog

Recently, surgeons and emergency room physicians at the Rocky Mountain Regional Trauma Center in Denver noticed a troubling trend. They seemed to be seeing cyclists with more serious injuries than in years past. Since many of the physicians at the hospital, a Level I trauma center serving the Denver metropolitan area, were themselves cyclists, they wondered if their sense of things was accurate.

So the doctors began gathering data on all cycling-related trauma admittances at the hospital and dividing them into two blocks, one covering 1995-2000 and the other 2001-6.

The data, which were presented in mid-October at the 2009 Clinical Congress of the American College of Surgeons in Chicago, revealed “some pretty alarming things,” said Dr. Jeffry Kashuk, an associate professor of surgery at the University of Colorado School of Medicine, attending physician at the trauma center and an author of the study. Over the years, the severity of the bodily damage, as measured by a standardized injury severity score, had significantly increased. The number of chest injuries rose by 15 percent, while abdominal injuries tripled. The typical length of cyclists’ time in the intensive care unit grew. Meanwhile, the average age of the injured riders had risen, from 25 to about 30, and when the researchers plotted the most recent injury sites against a map of the Denver area, they found smatterings of accidents along bike paths, but large clusters downtown.

“What we concluded was that a lot of these people were commuters,” Dr. Kashuk said, adding, “If we keep promoting cycling without other actions to make it safer, we may face a perfect storm of injuries in the near future.”

There has been an enormous push in recent years to increase bicycle ridership, in hopes of improving both individual health and the environment. Cities like Denver, New York and Portland, Ore., have added bike lanes, given away helmets and otherwise tried to lure more cyclists onto the roads. But the Denver study seemed to indicate that getting more people to ride meant more would be hurt.

But that is not necessarily so, a well-established body of counterintuitive science promises. This research, which has examined bicycle-riding patterns in the United States and in Europe, has found that in virtually every instance, when the number of riders on the road increases, the likelihood of accidents declines. This surprising result is known among its researchers as the “safety in numbers” effect, and it has been repeatedly documented. In Britain, for instance, the number of cyclists soared by 70 percent during the oil crisis of the 1970s, a 2002 report on cycling safety there pointed out, but the number of annual deaths among cyclists then fell.

Similarly, in the Netherlands, a nation that loves its bicycles, the level of bike use rose 30 percent from 1980 to 1990, while the number of cycling-related deaths declined by a third. Closer to home, when a California public-health expert compiled data about accidents involving cyclists and walkers in major cities in California, he found that, as his 2003 study reported, “the likelihood of an injury is not constant, but decreases as walking or bicycling increases.”

How can more cyclists mean fewer accidents? “It seems unlikely that people walking or bicycling obey traffic laws more” just because more of them are on the streets, the author of the California study wrote. “Adaptation in motorist behavior seems more plausible.” In other words, when more cyclists show up on the roads, car drivers become used to them and respond appropriately. As the British report pointed out, “common events are safe, and rare events are dangerous.” Making cycling safer, the report concluded, “ requires that it become more popular.”

There is a Catch-22 in that proposition, of course, and studies like the one from Denver underscore the issue’s complexity. In the early stages of increasing bike ridership, injuries may increase, as may their severity, since drivers will not yet be acclimated to the influx of two-wheeled traffic (and many of the early-adapter riders will not be attuned to the nuances of negotiating in traffic). At the same time, according to surveys conducted over the years by researchers at the Harvard School of Public Health, most people say that the primary reason they do not ride bikes is a concern for safety. So reports about an increase in injuries, even if it were ultimately short-lived, could blunt the rise in ridership, making those who do cycle less safe.

What, then, can be done? No solutions are easy, said Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health and an avid cyclist who, with others in his department, is studying how best to increase bicycle safety. “It’s definitely a good idea to promote bicycle riding for a multitude of reasons, foremost among them better health,” Dr. Willett said. “But as with any health-related intervention, there are benefits and side effects.”

Transportation experts cannot agree, for instance, about whether to segregate bicycle and automobile traffic, using concrete barriers along bike paths or creating separate bikeways. In the short term, such an approach should protect cyclists. But if if drivers are not given the opportunity to acclimate to riders, will it actually make it more dangerous for bikers in the long run? No one knows. “We need studies; we need data,” Dr. Willett said.

In the meantime, as more cyclists are taking to the roads but drivers and cyclists have not yet reached an accommodation, individual responsibility seems the best response. Bicyclists must obey traffic laws, an obvious prescription often flouted, at least according to a study in May of cycling behavior in Midtown Manhattan. It found that many riders ran red lights and illegally ribboned through traffic. Even more egregiously, an April epidemiological study of bicycle fatalities in New York City from 1996 to 2005 reported that alcohol was detected in 21 percent of the cyclists killed.

Finally, do not assume that, should you dutifully follow the rules, you are freed from constant vigilance. Individual driving behavior, no matter how many cyclists ride, will always remain unpredictable, if not perverse. Consider the results of a 2007 study from Britain, which found that, when cyclists skipped wearing helmets, drivers yielded more of the road to them while passing; if the cyclists did don their helmets, the drivers tended to crowd dangerously close.