Delhi has the maximum number of vehicles in India. The problem of air pollution was so serious in Delhi. So, the Supreme Court directed the government to take appropriate measure for reducing pollution caused by automobiles through (i) Switch over of public transport from diesel/petrol to CNG (ii) Phasing out of old vehicles (iii) Use of unleaded petrol and reduced sulphur content of diesel (iv) Fitting the vehicles with catalytic converters (v) Compulsory regular check-up of pollution emission of vehicles and enforcement of Euro II norms