China’s capital city is planning ventilation corridors to tackle the country’s air pollution.

Densely populated cities tend to generate more energy and waste heat. This results in a much warmer urban environment than in surrounding rural areas, according to National Geographic.

Xinhua reports that Beijing saw its worst smog spell from November to December of 2015, blocking views across the city and prompting authorities to issue a red alert warning. Measures to curb pollution have led to air quality improving only marginally, with 186 days of ‘up to par’ air quality in 2015, up 14 days from 172 in 2014, Xinhua reported, citing data from the Chinese Ministry of Environmental Protection.

To reduce smog, the capital is planning to build ventilation corridors. These are designed to relieve a city’s heat and pollution by improving urban wind flow.

The corridors will be created by connecting parks, rivers, lakes, highways and small building blocks. Five primary corridors — over 500 meters wide — will run from the northern suburbs to the south. Secondary corridors, measuring more than 80 meters, are also planned. The corridors will reportedly allow northern winds to blow through Beijing during severe winter smog spells.