Experts said the time period for severe pollution is over for this season.

The 'odd-even' car rationing scheme is unlikely to be back on Delhi's roads until next winters even if the Environment Pollution Control Committee's (EPCA) 'graded response action plan' for NCR kicks in immediately.

This is because the "maximum risk for high level pollution exists till January 14 generally," said Dr Dipankar Saha, additional director and head of the Air Laboratory at the Central Pollution Control Board (CPCB). "After Makar Sakranti, temperatures go up and pollutants gathered close to earth's surface disperse considerably. The next flare up, warranting enforcement of odd-even as per the graded response action plan, may occur after autumn 2017 only," he added.

The Centre had recently issued a notification authorizing the SC appointed Environment Pollution Control Authority (EPCA)- headed by former bureaucrat Bhure Lal and Centre for Science and Environment (CSE) DG Sunita Narain - to enforce the pollution combat plan in the National Capital Region.

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The plan suggested a slew of measures -including implementation of 'odd-even' and stopping entry of trucks into Delhi except for essential commodities and all construction activities - when pollution level reaches 'Severe +' or 'Emergency' level. This is when Particulate Matter 2.5 concentration in the city would cross a threshold of 300 ug/m3 or Particulate Matter 10 would go over 500 ug/m3.

It also recommended that the 'odd-even' scheme should have "minimum exceptions." When introduced in December 2015 by the AAP government, many categories of drivers including women and union ministers were exempted to convenience the public.

CPCB is already in the process of setting up a task force comprising officers of the Ministry of Environment and Forests (MoEF), NCR State pollution control boards, Indian Meteorological Department (IMD), etc. This will generate a daily average PM 2.5 and PM 10 figure for Delhi and NCR and communicate it to the EPCA.

Dr Dipankar Saha said, "It is actually good in a way that we will get few months' time to set up the whole machinery to enforce the plan up to 'Emergency' level." He added that the enforcement agencies would need to coordinate with four States - Delhi, Uttar Pradesh, Haryana and Rajasthan - to get the best results.

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"However, pollution-control measures as per the other levels - Severe, Very Poor and 'Moderate to Poor' - will have to be implemented anyway. This includes stopping usage of diesel gensets, hiking parking fee etc," he said.

Anumita Roy Chowdhury, head of CSE's Clean Air Campaign, said, "Even this winter the pollution level was not too high. If say, the graded response plan was already in action from 1 October 2016 to 13 January, 2017, only eight per cent days would have been in the 'Emergency' category."

A senior Delhi government officer said, "We are yet to take a call if we want to do episodic 'odd-even' car rationing in the form of a public exercise or drill, even if the graded plan does not warrant it."

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