Odd-even is not enough
Delhi leads the country in its air pollution. The annual averages in the national capital are three to four times higher than the standards of particulate matter. Even gaseous pollutants like nitrogen oxide violate the limits, which are generally under control in most cities in India. Consequently, a large population base is exposed to very high concentrations of toxic pollutants.
There are many factors that contribute to high air pollution concentration levels. On the one hand, there are sources within the city limits that have an immediate impact on residents. On the other hand, pollution is also spread from outside. In-house sources include vehicles both private, such as two-wheelers and cars, and commercial such as auto rickshaws, buses, trucks etc. As per source apportionment studies, the share of vehicular pollution is about a quarter of the total PM2.5 concentrations in Delhi. While heavy-duty vehicles (trucks and buses) contribute to about half of the PM2.5 emissions, two-wheelers have a one-third share. Cars make up for 10 per cent of vehicular emissions.
During peak summers, wind speed becomes an issue as well.The predominant wind direction is from North to North-west, and the emissions released in these upwind regions impact the air quality in Delhi after being transported by winds. Other important aspect which defines air quality in a region is meteorology. While rising temperatures and clear skies ensure more vertical mixing, higher wind speeds lead to more horizontal dispersion of pollutants. Evidently, more pollution is observed in winters when temperatures and wind speeds are low.
It was under these circumstances that the Aam Aadmi Party rolled out the odd-even scheme road rationing scheme twice this year. While the Arvind Kejriwal Government with a clear intention wants to address the pollution problem, there are certain limitations to this scheme. In January, when the first phase of the odd-even experiment was in effect, the national capital saw some reduction in congestion levels and a marginal reduction in pollution too.
In winters, even a marginal percentage reduction in pollution leads to a significant decrease in absolute PM2.5, as pollutant concentrations during this time are extremely high. However, in summers, when pollution levels are relatively low and the share of vehicular sources too is low, the impact of the odd-even scheme is bound to be less. Moreover, slowly but steadily, people try to negate the scheme by looking for alternatives.
Purchase of new cars, old cars, motor bikes can not only negate the emission benefits but may also compensate congestion levels. This is most likely to happen in a scenario when public transportation system is not yet reliable and attractive enough to the general public. A study conducted by the TERI university found that reliability and safety in public transportation systems are the two prime factors which affect the shift from private to public modes for residents in Delhi. Conclusively, the odd-even scheme can still be used as an emergency measure during winters when pollution levels are severely high, but regularising it may only reduce its impact unless the public transportation is improved and the sale of alternative vehicles are checked.
More importantly, just restrictions on cars cannot be relied upon for massive reductions in pollutant levels and bringing them within the prescribed limits. Efforts are required to control pollution from other categories of pollution too. With the introduction of BS-IV fuels in 2017 and BS-V fuels in 2019, not only new vehicles but also older vehicles will shift to best low emission technology. They can be retrofitted with tail-pipe control devices. Tail-pipe controls provide decent efficiencies with BS-IV fuels and perform best with the 10-ppm sulphur BS-V fuels.
Policies for this needs to be discussed and framed as early as possible so that maximum benefits of low sulphur fuels can be accrued. Also, the inspection and maintenance system needs to be strengthened to ensure reduction in emissions and appropriate performance of the new technology in the real world conditions. Importantly, actions are required for all different categories of vehicles, and also at a wider spatial scale than Delhi.
Towns in downwind areas like Ghaziabad, Noida, Faridabad are impacted by emissions released from the national capital. Conclusively, the whole NCR region demands a comprehensive air quality management plan which has strategies for control in different sectors. The plans need to be based on scientific studies and have to be updated every three to five years. Based on the plans, air quality targets needs to be defined for each year, and strategies have to be enforced to achieve them.