ABC News 3/30/2016
Metropolitan authorities on Wednesday temporarily ordered all cars to remain idle one day a week in response to this notoriously smoggy capital’s worst air-quality crisis in over a decade.
Until now vehicles have been exempt from Mexico City’s “no circulation” rules if owners obtain a holographic sticker from a smog-check center certifying them as lower-emission.
But the Environmental Commission of the Megalopolis, a cross-government agency comprising the capital and surrounding suburbs that together are home to more than 20 million people, said in a statement that all cars must now comply, even if they have the exemption sticker. Vehicles will also be forced from the roads one Saturday a month.