As countries try to slash air pollution and step up action on climate change, many are looking at a key culprit: tailpipes.

India in 2016 put into effect its first fuel economy standards for passenger cars and by 2021 is expected to have lowered planet-warming carbon emissions from new cars by 30 percent.

Mexico similarly launched pioneering regulations to cut emissions in 2014, focused on reducing pollution from its millions of automobiles.