The city of New Delhi has less than four months to convert all diesel buses to natural gas, following an order today by India’s Supreme Court. New Delhi has missed several previous court deadlines, and at least 9,000 of the city’s 12,000 public buses still rely on diesel fuel. The Supreme Court orders have sparked strikes by drivers of buses, taxis, and auto-rickshaws. Although compressed natural gas is cleaner and cheaper than gasoline, New Delhi has authorized only one company to supply it and drivers often wait in line for hours to fill their tanks. With 13 million people, New Delhi is the world’s 12th largest city and vies with Mexico City for the worst air quality.

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