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Bike share does not need helmets.

September 22, 2017

I guess people think I am tedious on this subject (people on Facebook think I am tedious on this subject), but bike share is very safe. By design, it can count the number of trips. We’re pretty good at counting deaths, too. In over 100 million trips there have been two deaths. (Death #1)

On “normal” bicycles, we’d expect to see 20 deaths in that many trips. In cars, we’d expect to see 9 deaths in that many trips. Instead, two. (As a sanity check on those rates, Canadian statistics are similar.)

If driving doesn’t need helmets, then bike share doesn’t need helmets. Don’t be distracted by “look at all the safety devices on cars, look at the safe metal cage” — with all those devices, driving is still 4 times as likely to kill you, and we don’t think it needs helmets (TBI is the cause or co-cause of death in about 40% of car crashes; car crashes are a leading cause of TBI hospitalization and death).

There are several reasons why this might be true.
Bike share bikes come with daytime running lights.
Upright posture appears to put your head at lower risk in a crash.
Bike share tends to require a credit card, and the bikes are sized for adults. Small children don’t have credit cards and thus don’t ride bike share.
Bike share tends to occur in cities and biking is safer in cities (“but wait”, you say, “driving is also safer in cities!” Yes, and that means it is more dangerous than the driving average in suburbs and rural areas, where we still don’t even discuss the need for driving helmets. If that’s not dangerous enough for helmets, then neither is bike share.) People riding bike share are almost never bombing down a mountainside, and almost never engaged in head-down bicycle racing or race training.

If you claim to pay the slightest attention to math, if you claim to take a rational approach to risk, this ought to be the end of the discussion. Does the CDC collect biased statistics? Two separate studies found similar car and bicycle crash-death rates for the US and Canada (with Canada slightly safer, as one might expect if they’d ever driven or biked in both places).

2 Responses to “Bike share does not need helmets.”

  1. Mike Kupfer Says:

    There are other considerations besides fatalities. I bought my first helmet after hearing the stories of 2 other CS students, both of whom had fallen while riding and broken their collar bones. I’ve never had that injury but I’m told it’s quite painful. One person was wearing a helmet, the other was not. The person who was not wearing a helmet had a concussion and as a result was not allowed to take painkillers for several days. The person who was wearing a helmet did not have a concussion and had a more pleasant recovery.

    I don’t remember the details of their spills, so some of the factors you mentioned (non-upright posture, high speed) might have been involved. But if I were to participate in bike sharing here in the Bay Area, I’d try to have my helmet with me.

    • dr2chase Says:

      This is true, but that’s not what I’m arguing. Most head injuries come from falls, apparently random falls. You could wear a helmet all the time to guard against those. Second most head injuries come from driving cars. Both cases, even though helmet wearing would help (for cars, it’s been measured), we’ve decided that the benefit is not worth the hassle. All those bad complicating things that would be made worse by a concussion, can also happen in falls and driving cars, but again, not worth the trouble to wear a helmet. I’m not argue that the helmets don’t reduce the risk — I’m arguing that we often decide that we prefer the risk to the helmet-wearing, if the risk is low enough.

      And if we’re rational about risk, then any activity where the risk is even lower would also not be worth the trouble of wearing a helmet. And that’s bike share — per-trip, three times safer than driving. Is per-trip the right metric? It’s not a terrible one — you put on a helmet, you do your trip, you take off your helmet, the main hassle is roughly per-trip.


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