It's end of the the road for diesel buses in Delhi. From Sunday (1st Dec) Delhi will have only CNG buses plying on its roads. The last batch of about 600 diesel buses will be phased out on Saturday(30th Nov). There are about 7400 CNG buses plying on Delhi roads. The impact of the changeover from diesel to CNG has been complex. City NGO, Centre for Science and Environment's director Sunita Narain said : 'The growth of air pollution has been arrested, if one looks at the suspended particulate matter in the city'.