They would be created by connecting Beijing's parks, rivers, lakes, and highways along with the capital's green belts, and possibly also by limiting the height of buildings.

　　Wang Fei, Deputy Director of the Municipal Commission of Urban Planning, says each of the corridors will be more than 500 meters wide, with some secondary ones over 80 meters wide.

　　北京计划驱散雾霾

　　"Five first-level and a dozen second-level ventilation tunnels will be built. There might even be third-level ones in the future. Based on the different conditions of the tunnels, we will conduct further studies with meteorological departments and other experts. Each tunnel will have a model. The aim is to ease the urban heat island effect and decrease air pollution."One corridor will run through the central axis of Beijing from Taiping Suburban Park in the north, via the Olympic Park, down to the Temple of Heaven, all the way through to the Beijing-Shanghai Highway at the southern end of the city.

　　Wang Kai, Vice President of the China Academy of Urban Planning and Design, says the corridors will act as an air passage, accelerating wind speed and improving the urban micro-climate.

　　"Geographically speaking, Beijing is located at the northern tip of the North China Plain, near the meeting point of the Xishan and Yanshan mountain ranges. Beijing's outlying districts and counties extend into the mountains that surround the city from the southwest to the northeast. The prevailing wind direction in summer is southeast while that in winter is northwest. Having ventilation corridors in Beijing's urban center will speed up ventilation and regulate the local micro-climate. "Wang Kai also says that Beijing should also consider curbing the number and height of buildings in the municipality's urban center.

　　"Wind direction and speed are uNPRedictable therefore we can't just rely on the corridors. I think we should also tightly control the number of buildings in Beijing's urban center and their height. If you go to downtown Tokyo, London and Paris, you'll find most buildings there have less than ten storeys. At the same time, we should also add more green space."By the end of next month, Beijing and its neighboring cities will start using uniform criteria when they issue pollution alerts, which will be categorized by Air Quality Index readings.

　　Response measures to alerts will stay the same although each city can decide if primary and middle schools should be temporarily closed.

　　The uniform alert system will first apply to Beijing, Tianjin and four cities in Hebei and then be extended across a larger area.

　　For CRI, this is Luo Wen.