After the air quality index (AQI) touched dangerous levels of 625 pushing the national capital back into the severe plus category on Sunday, Delhi and national capital region will implement the “odd-even” traffic rationing scheme, starting 8 am today. India’s capital New Delhi has been enveloped in heavy, toxic smog in one of the worst levels of pollution in recent years.

Nearly 200 teams of the Delhi Traffic Police have been appointed to ensure compliance and around 5,000 volunteers have been trained to create awareness about the scheme. According to the Central Pollution Control Board (CPCB), Delhi’s 24-hour average air quality index stood at 494 at 4 pm on Sunday, the highest since November 6, 2016, when it was 497. The pollution levels prompted the administrations in surrounding cities of Ghaziabad, Noida, Gurgaon and Faridabad to close all government and private schools till November 5. Thirty-seven flights were diverted from the Delhi airport due to low visibility caused by the thick blanket of smoke.

Delhi Chief Minister took to twitter to encourage citizens of Delhi to share cars and carpooling in order to follow the scheme which will also reduce the city’s pollution levels.

An AQI between 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’, 301-400 ‘very poor’ and 401-500 ‘severe’. Above 500 falls in the ‘severe-plus emergency’ category.

Prime Minister’s Office (PMO) on Sunday called a review meeting on air pollution in Delhi and its surrounding areas. A statement released by the PMO said that the Cabinet Secretary will be monitoring the situation with these three states on a daily basis. Chief Secretaries of the states have also been asked to monitor the situation in various districts round the clock.

Every winter, the mega-city of 20 million people is blanketed by a poisonous smog of car fumes, industrial emissions and smoke from stubble burning at farms in neighbouring states during this time of the year.

The Odd-Even rule is returning to the national capital for the third time and will continue till November 15.