Dealing with Mexico City’s rising smog levels
4 May 2016 Last updated at 00:42 BST
The air quality in Mexico City dropped to its worst level in 14 years this March – the city is home to more than seven million cars.
The BBC looks at some of the solutions being proposed for dealing with its air pollution.
How Paris is stepping up its drive against the car
By David Chazan
Paris is notorious for snarled-up traffic and cranky drivers – but cars are gradually being edged out as the city steps up a life-or-death battle to cut pollution.
The Indian capital, Delhi, has begun a second round of car rationing, aimed at curbing high pollution levels.
Private cars with even and odd number plates would only be allowed on alternate days from 15 to 30 April, Chief Minister Arvind Kejriwal said.
A fortnight-long trial from 1 January took more than a third of the city’s three million private cars off the road, easing congestion.