India’s Supreme Court has given New Delhi three days to come up with a plan to clean up the air in a city ranked by the World Health Organisation as the most polluted in the world. Successive local governments in Delhi have failed to check pollution from industry and increasing traffic. This is not the first time the court has passed such an order after local governments failed to build roads to ease congestion. About 52,000 commercial vehicles, excluding taxis, enter the landlocked city each day, more than double government estimates. Such vehicles account for about a third of the city’s pollution.