“The transport department had little option but to ask vehicle-owners to replace their two-stroke engines with four-stroke ones and then convert it to LPG,” a transport official said.

Soon after this, a gazette notification dated May 25, 2005 strictly prohibited the plying of auto-rickshaws and three-wheeled passenger vehicles within the Kolkata Metropolitan Area after September 1, 2005 unless they are LPG BS-2 emission standard compliant vehicles or LPG retrofitted vehicles. Later, the deadline of August 31, 2005 was extended to December 31, 2005 on the request of the state transport department. The state government, again, failed to meet the said deadline.

In 2007, environmentalist Subhas Dutta filed a PIL in the Calcutta High Court claiming that autorickshaws in the city were the highest contributors to air pollution. In the PIL, he stated that the pollution was caused due to use of adulterated oil.

Through a series of court hearings in 2007 and 2008, the state environment department issued a notification in July 2008 chalking out a detailed phase-out plan for the city autorickshaws. The three-wheeler was to be phased out in three stages — all two-stroke autos by December 31, 2008; all four-stroke autos not converted to clean fuel plying within the Kolkata Municipal Corporation area by March 31, 2009; all four-stroke autos not converted to clean fuel plying within the greater Calcutta area by December 31, 2009. The Autorickshaw Operators’ Association filed a plea in the court seeking extension of the deadline that was refused by the High court on December 23,2008.

Of the 20,000 autos plying in the city, around 76 per cent are two stroke ones. Earlier this year, the state government had worked out a package for auto rickshaws, which would be banned from plying after December 31, 2008.