Delhi to tighten NCR border checks under GRAP, divert non-destined heavy vehicles, stop/impound polluting and overaged vehicles, enforce PUC norms. New Delhi, Oct 25 (PTI) The Delhi government has stepped up coordination with neighbouring NCR districts to curb winter air pollution, with Environment Minister Manjinder Singh Sirsa on Sunday. Only electric vehicles, CNG and BS-VI diesel buses would be permitted to operate, subject to prescribed conditions.