Mexico City's Hoy No Circula: Restricting Car Travel to Abate Air Pollution (B)

The rapid, sprawling growth of the Mexico City megalopolis-combined with industrialization, a fast-expanding fleet of gas-fueled vehicles, and a location vulnerable to deadly thermal inversions-led to a serious air pollution crisis in the city in the mid 1980s. Having neglected air quality for many years, government officials prioritized it in the mid 1980s, attacking poor air quality with some energy and a five-year package of reforms to address the problem from different angles. They recognized, however, that most of these reforms would require several years, at least, to yield results. Eager to do something with more immediate impact-and keen, too, to signal to motorists the serious negative consequences of driving-they decided to add a driving restriction program to their package: the Hoy No Circula ("No Driving Today") program. This policy required all private car owners to refrain from driving one workday per week, based on the last digit of their vehicle's license plate. The simplicity of the approach was its selling point. It could be implemented almost at once at very little cost, and, policymakers reasoned, should result in an immediate 20 percent reduction in traffic, Monday through Friday. In fact, the idea was so appealing that many other developing countries followed Mexico's lead, enacting their own versions of Hoy No Circula in the years that followed. In this two-parter, the A case introduces Mexico City's air pollution problem at the time, and provides the rationale for enacting Hoy No Circula. The B case explains what happened once the policy was enacted, and how policymakers responded to some of its unforeseen consequences.