BS-III vehicles

The objective behind a cleaner fuel technology would not be achieved if older vehicles continue to flood the market, said Epca, a Supreme Court-appointed autonomous body that advises government on ecological issues.

The court also rejected the Centre’s argument that the BS-IV rollout only banned manufacturing and not the sale of the BS-III vehicles.

The biggest difference between the two is the emission of carbon particulate matter, a major air pollutant. While BS-III vehicles emit 2.30gm of carbon monoxide per kg of fuel, the emission drops to 1gm per kg in BS-IV vehicles.

Transition to BS-IV could lead to a substantial drop in particulate matter emissions. For instance, new trucks could see an 80% drop in emissions and cars by 50%, Epca told the court.

Similarly, hydrocarbon and nitrogen oxide emissions — a big concern for two-wheelers — could drop between 41 and 80%, depending on the engine size, it said.

The norms have to be followed by auto makers as well as fuel companies. The solicitor general told the court that BS-IV fuel would be available across India from April 1.

Industry would abide by the order, the Society of Indian Automobile Manufacturers (Siam) president Vinod K Dasari said.

The industry had been ready with BS-IV manufacturing since 2010 but the sale of these vehicles was not possible nationwide due to lack of BS-IV fuel, Dasari said.

India has set a deadline of 2020 to switch to BS-VI norms, giving a miss to stage V. But the leap, which will include technology upgrade, will make vehicles pricier – petrol cars by ~20,000 to ~25,000 and diesel ones could cost up to ~1 lakh more.