How a story on bike injuries got it so terribly wrong

That questionable study we mentioned last week that suggested that there are more head injuries in cities — including Minneapolis — where there are bicycle ride-sharing programs is looking even more questionable.

The researchers’ theory was that people don’t wear helmets for most rideshare rides and that accounts for the increase in head injuries.

As the NewsCut post mentioned, critics of that interpretation said the data actually showed that head injuries went down in rideshare cities, but we couldn’t see the data because it was hidden behind the paywall of the medical journal in which the research was published.

Now we can. Here is the data from the noteworthy “table 2” that led the study’s detractors to action.


Kay Teschke at the School of Population and Public Health at the University of British Columbia has looked at the original data and come up with the same conclusion the original commenters on the NPR site came up with: the study — or at least the reporting of it — is wrong.

There are still some questions from the data that need to be answered, notes Eric Jaffe at The Atlantic.

First and foremost is why total and head injuries declined in bike-share cities. The data, which show a correlation rather than a causal link between bike-share use and injuries, can only inspire speculation. One possible reason is that bike-share cities are benefitting from the “safety in numbers” effect; another is that bike-share cities also tend to build better bike infrastructure, which not only enhances safety but encourages riding.

The other question is why head injuries rose as a proportion of total injuries in cities with bike-share programs. It is indeed possible that bike-share users don’t wear helmets as often as non-bike-share cyclists, contributing to the relative rise, although if that were the case it’s quite strange that head injury severity would decline. It’s also possible that bike-share bikes are safer in general — with their heavy frames and wide tires — producing fewer total injuries that require treatment and thus making head injuries appear proportionately more frequent.

“The lesson, as always, is not that helmets aren’t safe. It’s still always a good idea to be careful when you bike, no matter what city you live in or what type of bike you ride,” Jaffe says. “Just be careful when you read and write about cycling, too.”

NPR has since revised the headline on its story to “Head Injury Risk Rose In Cities After Bike-Sharing Rolled Out,” which is certainly different from the original assertion that head injuries actually rose. It’s also a bit of a “duh” conclusion, given that risk always rises with an increase in any activity.

Why the critical eye to the story had to be made by readers/listeners rather than NPR editors and reporters remains an unanswered questions.