EPCA said the level of PM2.5 (fine respirable particles) pollutants in air had not exceeded 391 micrograms per cubic metre in January despite very low wind speeds on some days, whereas it had touched 606g/m3 during a three-day smog episode in November, and 524g/m3 in December. Air pollution is considered "severe" if PM2.5 concentration exceeds 250g/m3.

"It is notable that during days before the programme was started, pollution levels had increased when wind speed was low. This brings out the clear impact of the odd-even scheme on pollution levels," the EPCA said in a note.

The petitioners, however, pointed out that PM2.5 levels had remained alarmingly high during the odd-even scheme and peaked between 400g/m3 and 500g/m3—about eight times the safe standard and no different from other years.

Referring to the latest DPCC data updated till Friday morning, KarunaChhatwal, a petitioner, told the bench of Chief Justice G Rohini and Justice Jayant Nath, "There has been no reduction due to the scheme." Supporting Chhatwal, advocate Rajiv Khosla, president of HC's bar association and one of the petitioners, said Central Pollution Control Board's data showed worsening air pollution.

Without commenting on the overall reduction in pollutants, EPCA said levels of nitrogen oxides and particulates had reduced by up to 40%, possibly because many diesel cars were off the roads. "This indicates reduced exposure to toxic pollution from vehicles on roads, and close to roads," EPCA said. The authority cited two studies by US-based Health Effects Institute and University of California, Berkeley to stress that 55% of Delhi's population lives within 500 metres of roads, and pollution levels in this narrow zone are 1.5 times higher than the average for the city.

Making a case for continuing the odd-even scheme, EPCA told HC that while per capita emissions of car users in Delhi must have reduced, car occupancy had increased due to carpooling. Citing the draft IIT Kanpur report, it said vehicles were the second major contributor to PM2.5 after road dust. The same study has shown that diesel vehicles are the main PM2.5 emitters in the transport sector. "Delhi government must be permitted to continue with the odd-even vehicle rationing scheme and if these adverse weather conditions continue, our recommendation is that the programme should also be continued."

Amit Bhatt, strategy head for integrated urban transport at Embarq India, who has been following the odd-even schemes implemented in Beijing, Paris, Bogota and other foreign cities, said PM2.5 levels had declined quickly in those cities too. "There is usually a 15-20% reduction in traffic, and consequently some reduction in respirable particulate pollution," he said.

He, however, warned that a prolonged odd-even plan won't work as people will buy two cars to beat the ban, so the government must improve and increase public transport "so people don't switch back to cars."

Times View

Talk of going in for another round of odd-even is dangerous. What the Delhi government is doing is passing on the cost of its failure—primarily, to expand public transport—to a hapless citizenry. (We're not blaming Kejriwal on this count; the real culprits are those who came before him.) But to suggest that people are "for a change following rules" is facile—faced with a fine of Rs 2,000, do they have another choice? Besides, every study has shown that cars are far less polluting than two-wheelers and trucks. It's time the courts stepped in and put an end to this. Yes, many families own two cars these days, and if they're lucky to have odd- and even-numbered cars, they're probably quite happy with the lighter traffic and quicker commuting time. But not everyone in Delhi is as blessed.