The French capital has got a first-hand taste of what it's like to be Los Angeles: in the past week, Paris has emerged from a cold snap. Paris has enjoyed cool nights, and unseasonably warm days. Paris has not been visited by much wind. Paris can't breathe.
The BBC reports that a thick blanket of smog has settled over Paris, a result of pollution from automotive traffic and industry, and a combination of weather conditions much like those often seen in Los Angeles or Salt Lake City. On Friday the Parisian count of fine particles, that is so dangerous to lung health, is higher than in most Chinese cities on that same day.
But while Angelenos get to live with the smog, the Parisian authorities have called a state of emergency. They have not quite banned the use of private cars in the city, but have urged people to leave their cars at home and navigate the city using its excellent network of public transportation, which is complemented by vehicle share facilities.
To sweeten the carrot, they have made those facilities available free of charge throughout the weekend. The Paris Métro, RER commuter lines and tramways are free throughout the weekend. You can use bicycles of the bikeshare service Vélib' for free for a day, and cars of Autolib' are free for one-hour periods.
In addition, heavy trucks are banned from entering the city, and speed limits have been reduced from 130 to 110 km/hour on highways (or from 81 to 68 mph): this significantly increases fuel efficiency and decreases tailpipe emissions of pollutants.
Apparently, the pollution is not quite so bad as to call for a car-free weekend. This sounds like a radical a solution, since many European cities either have car-free Sundays scheduled periodically, and/or participate in European Mobility Week every September, when cities emphasize mobility by any means other than the car. It's when slow traffic occupies major cities and the mood turn very festive.