Pressure from the automobile industry is delaying implementation of tighter vehicular emission norms in cities across India. Though four-wheelers in 11 cities, including the four metros, switched from Bharat Stage (BS) III emission norms to BS IV on April 1, other cities supposed to make the switch from BS II to BS III norms have to wait. A draft notification of the government has proposed October 1 as the new date for implementing BS III norms.
http://www.downtoearth.org.in/node/644