After a disconcertingly smoggy weekend, wind and rain cleared some haze from Beijing’s skies on Tuesday. But with just a week and half left until the Olympic Games begin, officials are considering emergency measures to keep the smog at bay. The city has already kicked half the cars off its roads, halted construction, planted trees, and closed down some factories; officials said Monday that they may keep 90 percent of cars from driving, shut down more industrial operations, and discontinue special traffic lanes for Olympic VIPs. Many of the 10,500 athletes who will compete at the Games are taking precautions: several teams are training in Japan, Singapore, and South Korea instead of Beijing; the Japanese team will bring dust masks; the Australian Olympic Committee has given its athletes permission to withdraw for health reasons; the Canadian team will bring its own meteorologist; and Britain’s female field hockey players will wear red contact lenses to help them see more clearly in the smog.