Calling Delhi's odd-even scheme a 'farce', the NGT has said it cannot be implemented without its permission.
The AAP government announced odd-even from November 13 in view of alarming pollution levels, but experts say air quality might improve by then.
The previous two editions didn't do much to check pollution either, they said.
The NGT is likely to take a call on November 11.
During the odd-even scheme, private vehicles with odd and even registration numbers are allowed to ply on alternate days only.
The AAP government executed its first phase during January 1-15, 2016, and the second during April 15-30 the same year.
But the Central Pollution Control Board had said there was no evidence to suggest it had reduced vehicular pollution.
The capital is currently in the grip of a crisis: air quality index in some parts even touched 999 (anything above 400 is considered 'severe').
Schools have been shut till Sunday.
Experts have warned the pollution can kill as many as 30,000 people this year. Some say only evacuation might protect people.
The Delhi government announced odd-even during November 13-17 to tackle the problem.
The NGT had several questions for the government: it asked how much cars contribute to total pollution and how much one diesel-run vehicle pollutes compared to petrol vehicles.
"Also, why exempt two-wheelers from odd-even?"
If it wanted to stop pollution, why didn't the government publicize its destination buses like the odd-even scheme, it asked.
However, the NGT said it isn't stopping it yet.
Despite a well-connected metro network, Delhi lacks the requisite public transport facilities as needed by its burgeoning population.
The 5,600 government-run buses are grossly insufficient compared to the 11,000 buses that are needed as per expert estimates.
But Transport Minister Kailash Gahlot has assured getting additional DTC buses would be the "main component" of odd-even 3.0.
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