Context-The Delhi government will reinstate its odd-even scheme during November 4-15, 2019, announced Chief Minister Arvind Kejriwal

• The scheme, which has been the Aam Aadmi Party (AAP)-led government’s pet project to fight air pollution in the smoke-infested Delhi, was implemented twice in 2016. For two weeks, each time. But it remained controversial in its impacts.

Performance of previous odd-even phases

First leg: January 1-15, 2016

Success

• In its introductory phase, the odd-even scheme proved to be a successful measure in curbing air pollution in Delhi. During this time, Delhi experienced the lowest pollution peaks compared to previous high smog episodes in the winter, according to an analysis by Centre for Science and Environment (CSE), a New Delhi-based non-profit.
• This reduction in pollution was visible despite hostile weather conditions — no wind, temperature dip and western disturbance. While, before the odd even scheme in January, particulate matter (PM) 2.5 concentration increased whenever wind speed dropped, it fell after the scheme was actuated, added the analysis.
• Particulate matter and nitrogen oxide load from cars reduced by as much as 40 per cent while the scheme was operational, according to a status report by the Environment Pollution Control Authority (EPCA).
• The sale of petrol and diesel also dropped by 4.7 per cent and 7.8 per cent respectively between December 2015 and January 2016. This is another indicator of reduced pollution levels.
• There was reduction in the rate of improvement of air quality after the scheme ended, CSE readings noted.

Second leg: April 15-30, 2016

Mixed results

• The second phase saw some counter-intuitive trends. Air pollution levels tanked during the first nine days but then saw an unprecedented rise from April 22, according to air quality data released by the CSE.
• The PM2.5 levels increased by 23 per cent and PM10 by 22 per cent compared to the previous fortnight, reported IndiaSpend. Later, automobile companies used this analysis in a Supreme Court hearing to argue against stringent actions imposed on the automobile industry, reasoning that vehicles are an insignificant contributor to pollution.
• Using National Aeronautics and Space Administration satellite imagery, CSE found a sudden spike in crop fires in Punjab and Haryana from April 21.
• Even though the wind speed was conducive for low pollution levels, a sudden spurt in these fires along with garbage burning at Bhalswa garbage dump led to abnormally high levels of particulate matter.

Flaws of the scheme and solution

• Addressing infrastructural and policy issues are instrumental in making the odd-even scheme a success. Public transport in Delhi assumes a major role when it’s operational. According to a directive issued by the Supreme Court, Delhi needs 11,000 buses and it has around 5,500.
• The operating time of the scheme needs to be 24 hours instead the current 8-to-8 system, which incentivises commuters to reschedule their travels defeating the purpose of the idea itself.
• Prices of public transport need to be made negligible, it should provide last-mile connectivity and availability also needs to improve.
• Including two-wheelers in the scheme will also be a welcoming step, but it will increase the pressure on the already over-burdened public transport, said experts.
• They also believed that surge pricing for people opting to share cabs during the scheme period needs to combat through appropriate restrictions.
• The odd-even scheme should be treated as an emergency measure and should be implemented for not more than three to four days, said Chattopadhyay.

What exactly is Odd-Even Scheme

• The odd-even scheme is a car-rationing scheme borrowed from countries like China and many European nations, where it is believed to have brought down the pollution levels caused by vehicular emissions.
• Under the odd-even scheme, cars with licence plates ending in an odd number and even number are allowed to ply on alternate days, except weekends, but exemptions were earlier granted to women, VIPs, and two-wheelers.
• Simply put, vehicles with number plates ending in 0,2,4,6,8 will only ply on even dates like 4th, 6th, 8th and so forth, while the number plates ending in 1,3,5,7,9 will only ply on 5th, 7th, 9th and so forth.

Why is this Scheme needed?

• There are 3.1 million registered cars (as of 2018) plying on the roads of Delhi with 1000 new cars adding to the load every day on an average. 
• Delhi has been ranked on top of the World Health Organization’s ranking of the world's most polluted cities for several years, with vehicular and industrial emissions, dust from building sites, and smoke from the burning of waste and crop residue contributing to it.
• Delhi High Court once said that living in Delhi is like "living in a gas chamber", and can cause severe damage to health. 
• The Particulate Matter (PM) is worse among other forms of toxic gases and coagulates during winters to cause much trouble in Delhi. On the higher sides, the PM 10 can reach around 800 µg/m3 (microgram per cubic meters) in Delhi, at least 8 times more than the prescribed standards, which is around 100 µg/m3. The PM 2.5, which is much worse than PM 10 can reach 400 µg/m3, against the limits of 60 µg/m3.
• While pollution has gone down nearly 25 per cent in the last three years compared to the 2011-2014 period, studies show that pollution needs to be further cut by 65 per cent to meet clean air targets.

Odd-Even in other countries

The odd-even rule has been tried positively across the globe in various countries in the past. Some of the countries where the rule was applied and showed good results are -

• Beijing- Beijing has been the biggest influencer in the case of Delhi. Beijing has over 6 million vehicles on the road and both the cities have an identical population. During the 2008 Olympics, a system of road-rationing the licence plates was implemented in Beijing to check the rising pollution levels in the Chinese capital and the emission levels came down to 40 percent. For the first time ever in a long time, people were able to see a blue sky and the PM level dropped by 73.2% compared to the previous year.
• Sao Paulo- The Brazilian financial capital is one of the most populated cities in the world. They have been using the vehicle rationing system based on registration numbers for over a decade now, leading to lesser pollution.
• Oslo - Norway's capital Oslo, although has a very nice air quality, implemented such restrictions keeping the future in mind.
• London- Britain's capital implemented the vehicle exclusion rule during the 2012 Olympics to reduce pollution and congestion.

Challenges of Odd-Even rule

• There has been a wave of anger among certain sections of the society on the implementation of the Odd-Even rule and the political parties have also questioned the rationing system. The biggest challenge is that there hasn’t been a study on the impact of odd-even by any independent agency or the central government itself.
• Then there are pertinent questions like the availability of public transportation. Surely Delhi Metro is there, but not many people prefer Metro due to the last-mile connectivity problems. Also, not many prefer travelling on buses in the NCR region. Lastly, autos and taxis overcharge the travelers as seen last time.