The National Green Tribunal on Friday ruled that all buses and cabs travelling to and from the Delhi airport must run on Compressed Natural Gas, IANS reported. The court gave airport authorities and other agencies six months to convert all non-CNG buses and taxis plying at the airport to CNG vehicles.

The tribunal also directed the Ministry of Civil Aviation to ensure that green-wall technology, which is the use of vegetation to reduce airborne noise pollution, is used at the Delhi airport. The NGT also suggested having pilots avoid using reverse thrust while landing.

Air pollution in Delhi reached emergency levels earlier in November, after which the tribunal issued a series of orders to improve the air quality. On Wednesday, the court asked the Centre and the governments of Delhi, Haryana, Punjab, Rajasthan and Uttar Pradesh to come up with a solution to the problem of stubble burning, which is one of the primary reasons for the smog in Delhi at this time of the year.