Cycling Injuries Analysis in DC
I looked at a few years’ worth of data for DC (where I live) to try to figure out how risky cycling is here.
The Cycling commuters data was from the American Community Survey limited to the state of DC.
The traffic fatalities and injuries data comes from DC Vision Zero.
I’m going to ignore the “minor injuries” (which, to my understanding, includes minor scrapes, whiplash etc) and focus on major injuries + fatalities. I’ll call a one in a million chance of a serious injury a “microinj” (after “micromort” meaning a 1 in 1 million chance of death).
|Year||Regular Cycling Commuters||Minor||Major||Death||Microinj per year|
We don’t have 2020 ACS data (I guess they didn’t run it during COVID) and 2022 is not released yet.
Let’s also compare 2021 stats in DC by type of commute:
|Mode||Regular Commuters||Minor||Major||Death||Microinj per year|
It surprises me to see that regularly commuting by bike appears to be about as safe as driving, in terms of microinjuries per year. (2021 may have been an unusually low dip in injuries - if we assume 2022’s cycle commuter count is similar then we would get a post-COVID point estimate of closer to the pre-COVID numbers, up in the mid 3000s of microinjuries per year, which is a bit worse than cars but not a lot.)
Why could these numbers be wrong?
ACS surveyed commuters, but the thing we are trying to estimate is trips. There are a lot more trips than commutes and they’re of different modes. An example is that even if you commute by car, you are a lot more likely to just walk around your neighborhood to go to the grocery store or whatever (not as part of a “commute”). So that’s why I didn’t highlight the high apparent microinjuries-per-year of pedestrians above; most pedestrian trips are probably not commutes and so the true rate of pedestrian injuries/fatalities per trip is much lower. I expect this affects walking trips a lot more than bike/car, but it adds noise to all of them.
Can we back this into microinjuries per trip?
I can’t find data to suggest how many bike trips people take in DC, so I am just going to make up numbers here: For the ~7500 people who are regular bike commuters, they make 6 “commute” trips per week; then I’ll just squint and double that to capture non-commute trips. That adds up to roughly 5 million bike trips per year in DC. 25 injuries per year with 5 million trips is 5 microinjuries per trip.
But what about the benefits of cycling?
Cycling is a form of moderate exercise. Exercise makes you healthier and thus less likely to die. Per wikipedia’s entry on microlife, the first 20 minutes of moderate exercise (~ about 1 bike trip) is worth 2 microlifes. It’s harder to compare this against microinjuries, but to me this looks to be in the same very rough ballpark.
In DC, bike commuting seems safe-ish. About one in three hundred regular bike commuters will be seriously injured or die each year, which is about the same or maybe a little bit worse than driving; but this is roughly counteracted by the positive benefits of the exercise you get from cycling which you don’t get from taking a car.
If you’re prioritizing avoiding injuries at the 1-in-300-per-year level (which is a reasonable thing to be worried about, although I currently don’t worry about it myself) then you should take public transit for all your trips, which should be quite a lot safer.
If you’re prioritizing time spent commuting, you should probably bike, unless you find metro time pleasant or productive. I personally enjoy biking quite a lot more than any other form of transport, and it’s just about as fast as driving most distances in DC and is a lot faster than public transit!
I suspect this is misleadingly high, see “Why could these numbers be wrong” section ↩