A bench of Justice Madan B. Lokur and Justice Deepak Gupta stayed the November 11, 2017 order of the NGT after the counsel appearing for Delhi government contended that apart from the two-wheelers, they also wanted exemption for vehicles driven by women due to "safety" concern.

The NGT had directed that odd-even scheme, which is currently not in force in Delhi, would be applicable for all vehicles otherwise such relaxation would defeat the purpose of improving Delhi's ambient air quality.

Under the scheme, odd and even numbered vehicles are to ply on alternate days.

The top court while hearing the Delhi government's plea against the NGT order, also issued notice to the petitioner who filed the plea before the tribunal.

During the hearing, the apex court also asked the counsel appearing for Delhi government why there is no odd-even scheme in force now. At this, counsel replied the scheme would be implemented based on the level of PM10 and PM2.5 and the ensuing months of winter would be the time for it.

As per the Graded Response Action Plan (GRAP) for Delhi and the National Capital Region (NCR), the odd-even scheme comes into effect automatically whenever the particulate matter PM10 and PM 2.5 rises to 500 microgram per cubic metre and 300 microgram per cubic metre respectively for 48 hours.

Earlier, during odd-even scheme, exemption was granted to women driving four-wheelers due to safety reasons.