Significantly, the reduction in pollution was reported by Kejriwal for a period during which the odd-even scheme was not implemented in Delhi. The same scheme was earlier enforced by his government twice in 2016 -- first from January 1 to 15 and then from April 15 and 30.
The scheme, under which odd-numbered vehicles will be permitted to ply only on odd dates and even-number vehicles only on even days, is aimed at reducing the number of vehicles as they are seen as major pollutants.
Delhi is the only city in India to have seen the odd-even scheme, which was started in Beijing in 2008. Several other countries, including Paris, Mexico and Bogota too have used the scheme to curb pollution.
While making the announcement, Kejriwal said details of the scheme, to be implemented a week after Diwali, will be shared later.
According to the government data, there were 109.86 lakh motor vehicles on roads in Delhi as on March 31, 2018. Also, there were 598 vehicles per 1,000 population in 2017-18, up from 356 in 2007-08.
In the notification issued in December 2015, just before implementation of the scheme for the first time, the Kejriwal government had said Delhi has more than 90 lakh registered vehicles and the vehicular pollution has become a major source of air pollution in the city.
Under the scheme, the plying of non-transport four-wheeled vehicles -- cars and jeeps -- having registration number ending with an odd digit (1,3,5,7,9) was prohibited on even dates of the month and those having registration number ending with even digit (0,2,4,6,8) were prohibited on odd dates of the month. This was also for four-wheeled vehicles having the registration number of other states.
The restriction was applicable between 8 a.m. to 8 p.m. from Monday to Saturday.
The private cars and jeeps were the most impacted by the scheme. As per government data, between 2017 and 2018, cars and jeeps accounted for only about 30 per cent of the total registered mortised vehicles, whereas two-wheelers are about 64 per cent of total registered vehicles.
Also, there is a contradiction regarding the actual number of vehicles plying on Delhi's road as a large number of vehicles registered in Delhi are plying in the NCR areas and also the vehicles registered in NCR are plying in Delhi.
The government took the step in 2016 as Delhi suffered very bad days of pollution in December 2015.
While the air quality of the city remained more or less okay throughout the year, the winter days saw huge pollution, with the Delhi government blaming stubble burning in neighbouring states of Haryana and Uttar Pradesh.
The scheme was implemented for the second time between April 15 and 30 in 2016. The Delhi Metro and Delhi Transport Corporation (DTC) had increased their services both the time to accommodate the load of passengers. A fine of ₹2,000 was imposed for the violation of the rules.
There has been a mixed reaction from the experts and residents of Delhi about the scheme.
The Delhi government said according to a study on Delhi's Odd-Even policy by experts at the Energy Policy Institute of University of Chicago (EPIC) and that of Harvard University, the first term of the policy in January 2016 resulted in a drop in PM 2.5 levels by 14-16 per cent as compared to neighbouring cities -- Gurugram, Faridabad and Rohtak.
"Their recommendation was that odd-even policy is a very effective emergency measure, especially in winter months," Kejriwal said.
The Chief Minister said for 10 or 11 months of a year, Delhi's air remains better. "But every November, because of the smoke that comes from Punjab and Haryana, Delhi turns into a gas chamber. The Centre and these states are trying to prevent this from happening. But until that happens, we must take steps to protect ourselves from the toxic air created due to crop burning."
Kejriwal said the step can only be taken in emergency and that the government needs time to prepare for the scheme. Also, Kejriwal had claimed that in the past three years, air pollution has come down by 25 per cent, as he presented data and findings of Delhi Pollution Control Committee (DPCC) as well as Central Pollution Control Board (CPCB).
Between 2011 and 2014, the number of days with severe-plus levels (more than 300 micro gramme per cum) ranged between 20-40 days during the winter months. This has reduced during 2016-18 to less than 15 days, he said.
While Delhi has seen air pollution in winters in 2016, 2017 and 2018 as well, the Arvind Kejriwal government did not take any such steps to control the pollution.
This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.