Schools were shut down and traffic jammed the streets of New Delhi Monday after a Supreme Court ruling ordered half the city's public bus fleet off the road for failing to switch to CNG fuel, Reuters reported. The court, spearheading a drive to end pollution in New Delhi, rated one of the world's dirtiest cities, ordered all buses switch to CNG and set a three-year deadline in 1998, said the news service. More than 6,000 buses were taken off the road as a result of the deadline to phase out diesel buses, which the court had twice previously extended. Bus operators said they cannot afford the $10-a-day fine, which will double to $20 after a month, being levied by the court for noncompliance. Operators have decried the lack of CNG outlets, provided by the city administration, to allow them to switch fuels. Violence resulting from commuters protesting a similar court order last year has police officials bracing for a repeat performance.