In the NCR areas of Rajasthan, Uttar Pradesh, and Haryana, Delhi Environment Minister Gopal Rai called on the centre to impose a strict ban on buses running on subpar diesel. The minister revealed that all buses registered in these areas were BS III and BS IV vehicles during an unexpected inspection at the Kashmere Gate interstate bus terminal.

Rai stated that vehicular emissions contributed significantly to Delhi's air pollution. He noted that while buses in Delhi operated solely on compressed natural gas and electricity, those from neighbouring states like Haryana, Uttar Pradesh, and Rajasthan were using BS III and BS IV vehicles.

According to directions issued by the Centre's Commission for Air Quality Management (CAQM), starting from November 1, only electric, CNG, and BS VI-compliant diesel buses would be allowed to operate between Delhi and cities and towns in Haryana, Uttar Pradesh, and Rajasthan, included in the National Capital Region (NCR).

Rai emphasised, "While the CAQM has issued stringent directives in this matter, we urge the Centre to enforce a complete ban on BS III and BS IV buses being operated in the NCR areas of Haryana, Uttar Pradesh, and Rajasthan."

It was declared by the Centre in April 2020 that all cars sold in India must adhere to Bharat Stage-VI (BS-VI) emission regulations to reduce pollution levels. The Bharat Stage emission regulations impose legal restrictions on the amount of air pollutants, such as carbon monoxide and particulate matter that Indian cars are allowed to emit. These regulations primarily aim to enhance engine design, fuel economy, and pollution control.

Fuel companies supply fuel complying with BS-VI requirements, considered the world's cleanest fuel, while vehicle manufacturers produce cars that meet these new regulations.