Originally published By Somini Sengupta and Nadja Popovich | Illustrations by Tim Peacock for NYT | Nov. 14, 2019

At a time when most of humanity lives in cities, where do cars belong — especially the old, polluting ones that make city air foul for people to breathe?

That question has vexed city officials across the world. Many are trying a variety of measures to reimagine the role of automobiles, the machines that forever changed how people move.

The immediate motivation is clear: City dwellers want cleaner, healthier air and less traffic. The long-term payoffs can be big: Curbing transportation emissions, which account for nearly a fourth of all greenhouse gases, is vital to staving off climate catastrophes.