Divvy Week kicks off on Friday; 24-hour passes are free. It's a chance to try it if you're still skeptical, which… maybe still people are? Mary Wisniewski writes in the Tribune:

Oh, those Divvy riders — some of them look like organ donations waiting to happen.

No helmets. Riding like spawning salmon against the flow of traffic. Consulting tourist guides on busy streets, or riding in sightseeing pairs, oblivious to the aggravated commuters behind them.


But something surprising has happened — there have been zero fatalities in the United States since the first bike-share program started in Tulsa, Okla., in 2007, compared with the overall U.S. fatality rate of 21 per 100 million bicycle trips, according to a study funded and released last month by the Mineta Transportation Institute. The study also found that the rates of collision and injury among bike-sharing participants were lower than rates among regular bicyclists.

The Mineta study has been making the rounds, and attracting a lot of attention. The zero-fatality rate is perhaps surprising because you'd think it would happen just from random chance—and there was one serious near-fatality in 2014 in Chicago. But considering the general safety of the system compared to other forms of transportation, there was good reason to believe in its success from the beginning.


First, helmets. It might seem counter-intuitive, but there's a real debate about whether helmet use actually makes cycling safer. There's a lot of conflicting data on the subject, but the consensus, right now, is that while helmets are protective in the case of a fall, mandatory helmet use does little for safety overall. There's even an idea that wearing a helmet could increase risk-taking, as Ben Goldacre and David Spiegelhalter write in the British Medical Journal:

The impact on all cause mortality, and on head injuries, may be even further complicated if such legislation has varying effects on different groups. For example, a recent study identified two broad subpopulations of cyclist: “one speed-happy group that cycle fast and have lots of cycle equipment including helmets, and one traditional kind of cyclist without much equipment, cycling slowly.” The study concluded that compulsory cycle helmet legislation may selectively reduce cycling in the second group.

And the consensus among experts is having more safety-conscious cyclists on the road helps cyclists altogether. It's not just safety in numbers (like when motorists drive more safely because they are familiar with sharing the road with bikes), but compliance in numbers (which changes cyclist behavior by normalizing less risky cycling).

This idea came up in the expert interviews in the Mineta report (emphasis theirs):

While  some  experts  believed  casual  users  were  more  error  prone  because  of  less familiarity cycling with traffic, they believed this inexperience was compensated for by greater attention, defensive cycling, and motorists who were more forgiving of bikesharing riders. Most experts believed that bikesharing riders are less likely to wear helmets and more likely to ride on sidewalks when trails and bike lanes are unavailable. Most experts believed that the safest bicyclist on the road was an experienced bikesharing rider who wears a helmet.

An addendum: in my anecdata that comes from working on the tourist-heavy part of Michigan Avenue, Divvy riders do seem more likely to ride on the sidewalk; it can be mildly irritating, but I've become more sympathetic since reading up on the patchwork of cycling laws that makes Chicago an outlier when it comes to prohibiting sidewalk riding. It's legal, and even sensible, in a lot of places with poor or no bike infrastructure, high speeds, and little pedestrian traffic.

Another important point gets brought up in the Trib piece: Divvy bikes are sloooow. "The gearing on shared bikes does not allow users to go any faster than 11-12 mph," Wisnewski writes. In my experience riding Divvys (and sometimes getting passed by them) I think you can get them a little faster than that, but it's difficult to sustain and pointless to do so. Steven Vance measured himself and averaged less than 10 mph, a couple miles slower than his heavy-duty utility bike. By contrast, I average 12-14 on my big, slow mountain bike. And it's not the weight, it's the gearing.

Keeping it slow is really important, research shows. In a 1997 study, researchers found that risk of serious injury is increased at self-reported speeds over 15 mph, compared to speeds less than 15 mph. That same study found that risk for serious injury (and for neck injury) was not affected by helmet use at all.

It's fortunate that no one has been killed on a Divvy, but obviously being killed isn't the only concern; any kind of crash is. By those standards, the Mineta Institute found, bike share is safer than regular biking. But what about the alternative?

Cyclists sustain 1,461 non-fatal injuries per 100 million trips, the Mineta Institute says, compared to 803 per 100 million for being a passenger in a car. There have been 37 reported Divvy crashes in its history over 6.6 million trips. That comes out to 560 crashes per 100 million trips.

That number comports with bike-share data from New York—in 2014, there had been 40 injuries requiring medical attention over 10.3 million trips, or 388 injuries per 100 million trips. The Mineta Institute reports that, in Washington, D.C., from 2011 through 2013, bike-share riders took 226,062 trips per hospital injury—which calculates out to… 442 per 100 million. In San Francisco, it was 576.

Those back-of-the-envelope calculations suggest a ballpark figure is developing for bike share injury rates, and that it's actually lower than being a passenger in a car.

Divvy riders might "look like potential organ donors waiting to happen," but if so, it's because of our preconceived notions about safety. Being in a car is certainly being a potential organ donor waiting to happen, as Edward Humes writes:

Oddly, the most immediately devastating consequence of the modern car—the carnage it leaves in its wake—seems to generate the least public outcry and attention. Jim McNamara, a sergeant with the California Highway Patrol, where officers spend 80 percent of their time responding to car wrecks, believes such public inattention and apathy arise whenever a problem is “massive but diffuse.”


The death toll on America’s streets and highways during that same period since 9/11 was more than 400,000 men, women, and children. The traffic death toll in 2015 exceeded 3,000 a month. When it comes to the number of people who die in car wrecks, America experiences the equivalent of four airliner crashes every week.

Bike-share programs, by contrast, are not massive and diffuse; they're small, concentrated, and novel. When Divvy riders ended up on the Dan Ryan and Lake Shore Drive—in one instance resulting in a near-fatality—the incidents were media events. But as John Greenfield pointed out at Streetsblog, the LSD Divvy crash happened about the same time a wrong-way crash injured three on the Ohio feeder to I-90, and that barely registered. If you look past the coverage and its framing, and into the numbers emerging from the service, you might give Divvy a shot this Friday.