In a bid to further clean up the air in Delhi, the state government has decided to stop fresh registrations of all three-wheeler goods carriers, including those running on CNG, from September this year. In addition, operators have been directed to convert all existing petrol and diesel three-wheeler goods autorickshaws to CNG by March-end, 2005. The vehicles that are now powered by the clean fuel, government sources said will not be allowed to ply on Delhi roads.