Authorities in Mexico City announced new rules Wednesday that will require cars to remain off the road one day a week in a move to address the region’s worst air pollution in a decade.

The measure, which begins next week and will continue through the end of June, expands on a previous program that restricted high polluting vehicles on certain days. Now, cars will be required to stay off the road on one day a week in accordance with the color of a government assigned sticker, according to the Environmental Commission of the Megalopolis agency.

Mexico City has struggled with air pollution for the decades, but the situation had been improving in recent years as officials pushed through regulations on industry and transport. But last year a court ruling allowed an additional 1.4 million vehicles on the streets.

And with more vehicles comes more traffic and pollution. Increased traffic is a recipe for disaster when combined with over-populated streets (more than 20 million people reside in the greater urban area). Winter and spring tend to bring the worst air quality to the city—located in a basin—with few winds to push polluted air out of the city.

Air pollution has received attention in recent years for the millions it kills in fast-growing developing countries like China and India. But recent research has shown that air pollution continues to cause of a slew of health issues from lung cancer to obesity in more developed countries. And the death toll—while not as stark as in the developing world—still ranks in the tens of thousands in places like the U.S., Germany and Japan, according to a study in the journal Nature.

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Write to Justin Worland at justin.worland@time.com.