Public Transit is not Infinitely Safe

June 20th, 2023
cars, transit
I recently came across this tweet, screenshotted into a popular Facebook group:

Here's a truth bomb:

Take the U.S. city you're most afraid of, one with a very high murder rate or property crime rate.

If it has any sort of public transit, it is still statistically safer to use public transit in that city at ANY time of day than to drive where you live.

—Matthew Chapman, 2023-06-14

This got ~1M views, doesn't cite anything, was given without any research, and, I'm pretty sure, is wrong. While I'm a major fan of public transit, they've stacked this comparison in a way that's really favorable to cars, and it's not surprising that public transit doesn't make it.

Safety is a complicated concept, and risks are situational: in a car you're much more likely to be hurt in a collision, while on public transit you're much more likely to be hurt by another passenger. To get a clear comparison I looked just at deaths, which is also an area where we can get good statistics.

I can't find a listing of public transit agencies by homicide rate, but Chicago is a large city with a lot of homicides and they make their data available so let's look there. In 2022 there were 244M CTA rides. Downloading the Chicago Police Data and filtering to 2022 homicides on public transit, I see nine. This is 3.7 homicides per 100M trips.

(Note that the original claim was for any city, and there are dozens of US cities with homicide rates higher than Chicago's. I think it's pretty likely that at least one of these cities has a public transit system with more homicides than the CTA.)

To fairly compare this to the risk from driving, we need homicides per distance. How long is a trip? I can't find 2022 data, but the CTA's President's 2020 Budget Recommendations gives 4.1mi (1359M + 613M passenger miles divided by 230M + 249M trips). This means 0.9 homicides per 100M miles travelled.

I live in MA, and while 2022 FARS data isn't out yet, in 2021 there were 0.71 driving deaths per 100M miles travelled. While MA does happen to be the safest state for driving, MN, NH, and RI also have lower driving fatality rates than the CTA.

I'm not sure how to get to a place where we see fewer bold false claims, but a culture of giving sources, and supporting requests for them, seems like it would help?

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