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Proportion of head injuries rises in cities with bike share programs

(Andrew Harrer/Bloomberg)
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A few weeks ago, in honor of annual Bike to Work day, I asked a simple question about why those terrific bike share programs don't provide helmets to riders. There were a lot of understandable reasons -- hygiene, cost, liability -- but one thing all the cities I checked seem to argue is that bike share programs are very safe, much safer than, say, crusing around on your own bicycle. Their evidence was anecdotal, based on the tiny number of reports of injuries to cyclists who have taken millions of bike share trips nationwide.

Well, it looks like they are wrong.

In the first study of its kind, researchers from Washington State University and elsewhere found a 14 percent greater risk of head injuries to cyclists associated with cities that have bike share programs. In fact, when they compared raw head injury data for cyclists in five cities before and after they added bike share programs, the researchers found a 7.8 percent increase in the number of head injuries to cyclists.

When they looked at the same data for five cities that don't have bike share programs, the number of head injuries had declined a bit, by 2.3 percent.

"I would personally suggest folks err on the side of caution and use safety devices like bike helmets," said Janessa Graves, an assistant professor at Washington State's College of Nursing, who led the study, published online in the American Journal of Public Health. Researchers from the University of Washington School of Medicine also participated.

"Crashes can happen to anyone -- tourists visiting the city, children, seasoned cyclists who ride 200 miles a week," Graves added.

Even though a large body of research shows that bike helmets prevent head injuries, no U.S. bike share programs provide helmets. Seattle -- where the law mandates helmets for all cyclists -- and Boston are planning to roll them out soon. Both will use vending boxes that operate much like the bike share stations themselves. With the swipe of  a credit card, riders will be able to take a helmet from a box and return it when they're done. After each use, helmets will be picked up and taken to a warehouse for cleaning and inspecting before they are returned to the kiosks.

But most cities -- including New York, Washington and Minneapolis, where bike share programs have proven quite popular --have no plans to offer helmets. Many encourage riders to use their own helmets, and some subsidize their purchase or even give them away. On Wednesday the Dallas City Council eliminated helmet laws for adults, saying it would increase ridership of the bike share program.

Graves's team looked at aggregated data for Montreal, Washington, Minneapolis, Boston and Miami Beach before and after they started city bike share programs. The team did not get a breakdown of injuries for each city. The researchers compared the numbers with statistics from Vancouver, New York, Milwaukee, Seattle and Los Angeles (New York hadn't yet begun its bike share program at the time.)

They noted that in Boston and Washington, one count found that only 19.2 percent of bike share riders wore helmets, compared with 51.4 percent of other riders. In New York, 85.3 percent of bike share cyclists did not wear helmets.

"The conclusion of our study — that [bike share] implementation is associated with increased odds that a person admitted for a bicycling-related injury would have a head injury — is likely attributable to the low propensity of [bike share] cyclists to use helmets," the researchers wrote.

The limitations of the study design prevent the researchers from saying outright that bike share programs have caused an increase in head injuries (emphasis mine). For one thing, their data come from trauma centers, so they are biased toward severe injuries. And because the researchers did not get patient-by-patient information, it was impossible to determine which individual was a bike share rider and which one wasn't.

But Graves said the strong correlation makes it very clear that bike share programs should provide helmets from the outset. "You rent a car [and] there are seatbelts in the car," she said. "You don't have to advocate for them. They should be part and parcel of the program. I can definitely stand on the soapbox and say every bike share [program] should have helmets available."

Read more:

Why don't bike share programs offer helmets?

America forgot about bikes. Now it needs them more than ever

Why you should always wear a helmet, in one chart

Biking to work from the suburbs: it's not so easy

Note: The headline on this post has been updated.