During the 1980s, Mexico was known worldwide for its air quality problems. Mexico City, in that time, was considered the most polluted city in the world. Nowadays, despite having four times more vehicles, authorities have reduced air pollution concentration by more than 50% through a public policy integrated approach.
The link below includes a package of materials on what enabled this transformation, including a webinar that "discusses the history, public policies and challenges that Mexico has faced in terms of its private vehicle fleet management and how Mexico’s cultural and socioeconomical proximity makes its experience particularly interesting given the possibility of replicability,"; analyses of Mexico's automotive fuel economy policy; and data on air pollution in Mexico City, among others.