Pollution spikes during Delhi's odd-even experiment: The odds are even to clean the air in our cities

The pilot phase of the much publicised odd-even scheme in Delhi is now over. Besides Delhi, comprehensive plans are urgently needed to improve air quality across several Indian cities, such as Patna, Gwalior, Raipur, Ahmedabad, Lucknow, Kanpur, Ludhiana and Amritsar. Although policy interventions primarily target air pollution, it is important to note that traffic congestion has significant economic costs to society .How did Delhi fare on metrics of air quality and congestion ­ and what lessons should other cities draw from the experiment?
The stationary air pollution monitors of the Delhi Pollution Control Committee (DPCC) indicate that average (ambient) PM 2.5 levels increased from 216 µg m3 (26 ­ 31 Dec) to 331 µgm3 (1 ­ 6 Jan) and subsequently declined to 308 µgm3 (7 - 11Jan). As per the Central Pollution Control Board (CPCB) PM 2.5 levels that exceed 250 µgm3 correspond to an Air Quality Index of `Severe'. These levels affect healthy people and cause greater distress to those with existing heart or lung disease.
However, a spike in air pollution is not a predictor of failure just as a decline does not indicate policy success. This is because, in the short term, air pollution levels are dominated by meteorological conditions such as winds, rain and temperature.

While establishing a relationship between reduced car numbers and pollution levels is tenuous, the impact on traffic and congestion is purely a function of compliance levels. In order to understand the traffic mix during the odd-even experiment, the Council on Energy, Environment and Water (CEEW) monitored traffic volumes at five important stretches across New Delhi for three weeks (the week before and two weeks of the implementation). In the morning peak (9 am ­ 11 am) we observed that overall vehicle counts increased (by 10%) in the two weeks of January , as compared to the last week of December. However, taxis, 2-wheelers, 3-wheelers and private buses contributed significantly to this increase. The increase ranges from 12% for 3-wheelers to 138% for private buses. This does suggest increased use (or availability) of these alternate modes of transport.

However, the number of private cars remained unchanged.Anecdotal experiences (documented in social media) suggest that commuters experienced lesser congestion on the roads. Congestion data (as recorded from Google Maps), on the other hand, suggests that the travel times were not statistically different between the last week of December and the first week of January .The available metrics are confounding and no definitive conclusion can be made, on the impact of the scheme on traffic and congestion as well. One conjecture is that the baseline chosen for comparison (last week of December) does not represent typical Delhi traffic.

What can other cities learn from this large social experiment?
The absence of conclusive evidence is in large part due to the lack of precise measurements over longer periods of time and across locations. Such short-term policies must be evaluated in a robust framework that focuses on improved measurement at its core.

Despite the short lead time available to prepare for a full-scale monitoring, we also installed low-cost pollution sensors at five locations. We find that the readings (for PM2.5) closely follow those from DPCC (located in the vicinity of our sensors). There is a need to create a network of such low-cost sensors across our cities, and to make residents aware of pollution levels in their respective localities.

Secondly , we need to have more regular source apportionment exercises to understand the changing contributions to pollution from different sources such as waste burning, industrial kilns, road dust, construction, power plants, etc., besides vehicular pollution.In the ideal world, we should be able to characterise the sources of pollution in real time. It would then be possible to understand whether the contribution from vehicles to overall pollution declined due to such policy experiments.

This information would be useful for policymakers to address local area sources of pollution, and empower citizens to take precautionary measures when pollution levels spike. Delhi's experiment, therefore, remains instructive in the bigger battle against pollution in India.

The writers Hem Dholakia and Karthik Ganesan are researchers at the Council on Energy, Environment and Water , New Delhi.

(Source: 2016-01-19 The Times of India, Kolkata)