Paris air pollution: Is car ban a gimmick?
17 March 2014 Last updated at 13:50 GMT
Hundreds of police are monitoring traffic in Paris to ensure today only car number plates ending in odd numbers are driven on the city's roads.
Only motorists with cars that have odd-numbered registration plates should use their vehicles on Monday. On Tuesday, if the restrictions remain in place, it will be the turn of those with even-numbered plates.
Hugh Schofield observed police pulling over motorists on the western edge of Paris.
He said that most people were observing the ban, but as pollution levels in the city were already dropping, some people considered it "a PR gimmick".