Each day, at least under normal circumstances, residents of Mexico City take 17 million rides in peseros—a fleet of green-and-white vans or microbuses that are part of the city’s informal transportation system. The peseros—30,000 strong—are a world of their own. They can be crowded. Some blast music. They serve areas of the city underserved by other forms of public transportation. They serve more riders than all the city’s forms of public transportation. But there’s one major problem. There was no map whatsoever. “The only way of actually figuring out how…
