In its continuing effort to cut pollution in Delhi, the local government has introduced the second round of the Odd-Even scheme, where odd numbered cars (non-CNG, non-taxi) run on odd numbered days, and even numbered cars on even numbered days. This will apply between 8am and 8pm every day from the 15th of April to the end of the month.

However, restricting half the private vehicles in the city itself cannot have a large impact on pollution (PM2.5) levels, as I discussed in an earlier piece (short answer: small share of pollution by private vehicles, and unfavorable geography and regional meteorology of Delhi). Nonetheless, a study by the University of Chicago claimed that the first round of the scheme (1st to 15th of January, 2016) did have a marginal effect (10-13%) to curb pollution.

In spite of this study, there have been disagreements on the effectiveness of the scheme. However, commentators did agree that there was compliance by the residents of the city in the first round; enabled in part due to the Rs. 2,000 fine.

More importantly, the scheme "succeeded" because the residents of the city themselves understood the importance of doing something - anything - to curb pollution. Humans may not have inbuilt PM2.5 sensors, but we do infer something is wrong when the sky is grey, when visibility is low, when everyone and their uncles have a bad cough. If Odd-Even can bring us clearer skies and get rid of our coughs, let's do it!

In a very sunny April, however, this does not hold true anymore. The flu season has passed: coughing is rare. Particulate matter has absorbed heat from the summer sun and risen to higher altitudes - then been carried away by the summer winds. The skies are therefore clearer, visibility better. The human mind has been tricked into believing things are okay. We're not really feeling the need for Odd-Even this time. So what if PM2.5 levels are still very high - most of us can't feel it in the absence of other indicators.

What will the public opinion be this time around if substantial gains are not made, especially those that are not visible? Time will tell. For now, there have already been reports of motorists pasting CNG stickers on their petrol and diesel cars to escape the rule.

While the long run solution to pollution is rooted in pricing (as I had discussed here), my preferred short term solution to a public health emergency caused by air pollution is the selection of a 'no tolerance' threshold of PM2.5, beyond which all schools, malls and non emergency institutions will be shut for - say - three days after the threshold was breached. Additionally, all trucks using Delhi as a thoroughfare would be banned from entering - regardless of impact on commodity prices or the pain it may cause to transporters. After all - if it really is a public health emergency (and it really is), then half-baked measures like Odd-Even will just not cut it.