In India’s Capital Delhi, a rule has set a ban on Diesel Cabs for a purpose. The initiative aims the improvement of air quality in the city which is said to be the world’s most polluted capital. India’s top court on Saturday ordered taxis run on the dirty fuel off the city’s roads. The orders refused industry’s requests for more time to switch to CNG.

There are many taxis in the city which run on CNG, but the ban will impact on traditional cabs and few working for Uber and Ola services. The Supreme Court has been pressuring authorities to reduce dangerous levels of haze and dust that choke the city.

Frustrated and irritated taxi drivers have blocked the key intersections in Delhi and Gurgaon on Monday as a protest. Balwant Singh, who heads a taxi union of 500 members said, “You can’t have knee-jerk solutions to long-standing problems.”

Drivers said that they knew no technology to switch from Diesel to CNG and instead being forced to buy new taxis. A 2014 World Health Organisation survey of more than 1,600 cities ranked Delhi as the most polluted, partly because of the nearly 10 million vehicles on its roads.

The ban by the court left around 1 million cars off the roads in Delhi.