Half of Beijing’s cars will be taken off the roads in a plan announced Friday by officials, the Wall Street Journal reported. Beijing’s Environmental Protection Bureau said cars will be allowed on roads on alternating days, depending on even- or odd-numbered license plates, starting July 20 and ending September 20. The measures are being implemented to ensure clean air for the Olympics. As a result, about 45% of Beijing’s 3.29 million cars will be taken off the roads and an estimated 4 million extra public-transportation users will be added. The plan had been rumored for several months.