Free Bike Share! Free Public Transit!
And all you need to make these fine things happen is to have your air so polluted by cars that authorities get desperate. Oh, and they are also temporarily reducing the number of cars on the road: BBC News - Paris restricts car use after pollution hits high
So, for the next few days, Paris will restrict cars by plate number, offer free public transportation and free bike shares and positively choke on their engine exhaust.
For what it's worth, Milan, Italy has done a few car-free Sundays in the past for the same reason. When their air becomes overly toxic for twelve straight days, they don't allow cars to operate in the city from 8:00 AM to 6:00 PM on the ensuing Sunday.
While these are baby steps in dealing with one of the more visible problems of car dependence, they are steps that the US has not yet taken. I'm impressed that some Europeans are willing to acknowledge that cars have huge impacts and, by implication from their actions, much car use is entirely discretionary.