Recap: Delhi’s #OddEven plan, in hindsight

Late last year, Delhi’s Chief Minister, Arvind Kejriwal, announced a measure to tackle the severe air pollution crisis in the city. The proposal was to implement an odd-even plan for private cars on Delhi roads: cars with odd numbered registration plates would be allowed to ply on odd dates and those with even numbered registration plates allowed on the other days. There was an exemption list that included single women (or with children), public vehicles, medical emergencies, etc. This was to be piloted for a period of fifteen days, starting on 1st January 2016.

For a detailed account of how the city dealt with this rule, see here.  An excerpt:

During the odd-even period, the use of cars fells by 30 per cent while those car-pooling went up by a whopping 387.7 per cent, indicating the success of the government’s push towards that option. Delhiites using private auto-rickshaws went up by 156.3 per cent compared to the period before odd-even, while Metro use went up by 58.4 per cent.

On average, the respondents’ took 12 minutes less to commute from home to work during the odd-even period. Car and bus users reached their workplaces 13 and 14 minutes faster during the 15-day period

I will come to the outcomes of this pilot in just a moment. Outcomes aside, the Delhi government’s Odd-Even plan has yielded a rich bounty. It sets the template for citizen engagement with a public policy reform experiment: heightened awareness regarding the core issue, mass participation, intense public scrutiny, and a data-driven discourse. Let’s take these one-by-one.

Heightened awareness: From the Delhi High Court downwards, it is widely acknowledged that this government move has made pollution a talking point, and increased general awareness. Odd-Even has consistently trended on Twitter (the barometer of our times of how important a topic is) and has sparked numerous prime-time slanging matches. No doubt, there is also a haze of misinformation, but mostly, people are now hearing more about air pollution, how it affects their health, and what the various ways to deal with this problem are.

Mass participation: Largely as a result of the above, citizens in Delhi have demonstrated an overwhelming level of compliance with this experiment. I do not believe that just the fear of fines was sufficient to bring about this level of compliance. People have participated in solidarity with the scheme, partially out of their concern for the levels of air pollution, and also possibly, a curiosity to see if the experiment will yield any results. Either way, this experiment would have been a non-starter without this level of mass participation.

Intense public scrutiny: Just as much as commuters in Delhi have participated in the scheme, a wider population has actively dissected this experiment and have come out on both sides of the divide. This set of observers and analysts have highlighted implementation challenges, bringing out data on current and historical pollution levels, gathered and presented from multiple sources – government and non-government – this has been a public policy enthusiast’s dream come true. Heavy public participation, accompanied with this level of public scrutiny, makes for an ideal public policy reform experiment.

Data-driven: The resolution of the debate over the effectiveness of the Odd-Even plan has to rely on data, and what is available currently is not all robust, or scientifically well-informed. But in order to measure impact, hard data will have to be collected, and analysed, before a conclusion can be reached regarding the effectiveness of the scheme. One could also look at data on the numerous indirect and unintended benefits – decongestion is a prominent one, for example. To the quantitative data on pollution readings, one can add the qualitative data on people’s perceptions, attitudes and behaviours.

The reality of policy experimentation

Resistance to public policy reform, and experimentation ranges from the gentle to vitriolic. Politically, one can argue both sides of the coin – either that this just a political gimmick, or that the success in implementing the experiment reveals how strong public support for Aam Aadmi Party and Arvind Kejriwal continues to be. Reactions to the Odd-Even policy also reflect entrenched positions, many of which are political and motivated, but importantly, not necessarily just so. This is important – a public policy reform will be subject to serious criticism, not just motivated by ‘interests’, but stemming from genuinely opposing ‘ideas’. Those initiating a reform must be prepared to ‘learn’ – trial, review, tweak, and trial again.

Evidence trickles in

Over the last fortnight, researchers Michael Greenstone, Santosh Harish and Anant Sudarshan were collecting hard data on how the pilot fared. They find that the Odd-Even plan reduced pollution by significant levels in Delhi. The headline: this study finds there was an 18% reduction in PM 2.5 due to the pilot during the hours that the rule was in effect. The effect size is truly staggering, and is quite unusual for studies that use such rigorous methodology to look at the impact of policy interventions.

Starting January 1, while absolute pollution levels increased both inside and outside Delhi (for atmospheric reasons, as noted by other commentators), the increase in fine particle levels in Delhi was significantly less than in the surrounding region. Overall, there was a 10-13 per cent relative decline in Delhi.

…Around 8 am, the gap between Delhi’s pollution and that in neighbouring regions begins to form and steadily increases until mid afternoon. As temperatures begin to fall, and pollution is less likely to disperse, this gap starts to close. We see another small gap emerge between 9-11 pm, which probably reflects the new limits on truck traffic in Delhi, which also came into force on January 1. Soon after midnight, the gap closes, and Delhi and neighbouring areas show similar pollution patterns until 8 am comes around again. When focusing just on the hours that the odd-even policy was in effect, our estimates suggest that particulates pollution declined by 18 per cent due to the pilot. 

The methodology and analysis is set out in greater detail here:

We compare the changes in PM 2.5 concentration levels before and after the program in Delhi monitors and outside Delhi in the NCR: Faridabad, Gurgaon and Noida. While the odd-even program was in place for commuters from these cities to Delhi, the odd-even program was not directly implemented there. If anything, the impact on the commuters makes our estimates lower bounds to the true impact.

In doing this, they addressed a glaring oversight that journalists were earlier making – of taking into account, what would have happened in the absence of this pilot and comparing that with Delhi. Using a counterfactual and a difference-in-difference approach, the researchers are able to conclude that the levels of pollution in Delhi were indeed lower during the fortnight that the Odd-Even plan was implemented. Thus, while debates raged in the mainstream media, social media, and street-corners over the success and failings of this scheme over the two weeks of implementation, with the last piece – hard data – coming in, we truly have a case worth studying! Delightfully, the study has also silenced those who had waded in on the backs of unfounded methods and faulty data.

What next?

What one needs to consider is also whether this arrangement is sustainable in the long-term? Perhaps not, as has been the experience in other cities, unless Delhi sees collective action at an unprecedented level (phasing out old cars, people agreeing not to buy second-hand cars, etc). But while you cannot change the weather, and it may be difficult to stop farmers from burning crop waste in the short-term, the success of Odd-Even presents a new and effective tool – an option that can be implemented to bring down peak air pollution, or neutralise at times when the weather is most unfavourable.

The Delhi government should remember though that without serious efforts to expand and improve public transport, and introducing measures such as congestion pricing, or other forms of pollution taxes, vehicular pollution will not be controlled. Governments or leaders who claim to have all the answers probably aren’t the ones who would be open to trial and learning. As the researchers say:

More generally speaking, governments need to accept that we don’t have all the answers to policy problems and adopt a culture of trying out new ideas, testing them carefully, and then deciding which ones to adopt at scale

So what next?

It is often said that we get the government we deserve. Citizens in Delhi have participated honestly in a worthwhile public policy experiment. While the final outcomes will be ascertained as more data is collected and analysed, it is clear that problems like pollution can only be tackled with a critical mass of people coming together; collective action that can look beyond personal inconvenience. So the biggest gain from the Odd-Even plan would be a willingness to participate in experiments in collective action – a citizenry that is aware, engaged, and willing to work together with its government to find solutions to its problems.

In return, what they deserve is a government that is committed to finding answers to difficult questions – in this case, a government that is willing to explore all possibilities to devise a set of interventions that can tackle the scourge of air pollution in Delhi. Here’s hoping we see many more of such ideas…and in the meantime, the Delhi government deserves a wide round of applause.


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