Passenger wear masks at a subway in Beijing, Dec 8, 2015. The capital has issued its first-ever red alert for smog on Monday, which will last from 7:00 am Tuesday to 12:00 midnight Thursday. The red alert imposes the toughest restrictions on activities that may contribute to the pollution worsening, including a ban on the use of half of the city's cars. These measures increase the demand for public transport. (Photo: China News Service/Zhai Lu)
