The Crit'Air system was introduced in 2017 and assigns a number to each vehicle based on how polluting it is. But the Crit'Air system hasn't just been rolled out so drivers get to put a new sticker on their windscreens. So in the recent heatwave in July vehicles with Crit'Air number 3 and above were banned from inside the A86 outer ring-road in Paris. But the Crit'Air system isn't just enforced to help cut emissions during a heatwave. The same will apply to the outer suburbs in Paris where currently only vehicles with Crit'Air stickers number 5 are banned.

Source: The Local July 26, 2019 13:52 UTC