Beijing will reportedly be the Chinese city with the toughest vehicle emissions standards beginning in January 2017.

The Beijing Municipal Environmental Protection Bureau says that it wants to raise the bar for diesel and gasoline engine pollutants, which will be called the “Beijing Six” standards. It’s a major initiative as the smog-choked city aims to drastically cut vehicle emissions, as reported by the official Xinhua news agency.

The new “Beijing Six” standards will cut car pollutants by an additional 15 to 20 percent in the city, Xinhua reported, quoting a researcher with Beijing’s environmental protection bureau. “Beijing Six” will allow for a maximum sulphur content of 10 parts per million (ppm). It also requires a lower level of other pollutants such as Benzene and PAH (polycyclic aromatic hydrocarbon) compared with Euro V specifications.

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In addition, China’s “National Five” standard, equivalent to the Euro V specifications, will be implemented nationwide in January 2017. The “Beijing Six” standards is considered to be an improvement over China’s national five standards that are only used in more economically developed eastern provinces.

Diesel burning trucks and passenger car emissions have been a major contributor to Beijing’s persistent smog problem. On May 20, Beijing’s municipal government said it would remove from its streets more than 400,000 trucks and mini buses in 2016 and 2017 that burn low-quality high-sulphur fuels.