This may not work so well

Beijing Bans Cars to Clear Air for Games
They tried something like this in Mexico City once, banning cars on certain days based on their license plate numbers. (I think they only banned one tenth of the cars each day.) It actually increased pollution a little. Many people just went out and bought another car to drive on their off days. The real problem was, what they usually bought was a cheap, old car that polluted much more than their regular one.

Maybe conditions are different in Beijing. Maybe most drivers there can't afford a second car, or maybe there just aren't that many old clunkers for them to buy. But I would not be the least bit surprised if this scheme fails to reduce air pollution the way the officials think it will.