Before he became a public transportation consultant, Jarrett Walker pursued a Ph.D. in literature; as he observes on his website, he “is probably the only person with peer-reviewed publications in both the Journal of Transport Geography and Shakespeare Quarterly.” Walker is also likely to be the only contributor to either journal whom Tesla CEO Elon Musk has publicly called an “idiot.”

That viral exchange occurred in 2017, after Walker criticized Musk for dismissing transit passengers as “a bunch of random strangers, one of who might be a serial killer.” The kerfuffle left an impression: A chapter in Walker’s newly revised book Human Transit: How Clear Thinking about Public Transit Can Enrich Our Communities and Our Lives is titled “A Bunch of Random Strangers.”