There seems to be no early end to the argument on whether the odd-even scheme implemented by the Delhi Government in January 2016 was a success or not.

Representational image. PTIRepresentational picture. PTI

A new research study, published in the journal Current Science, signals that the rule did not result in a reduction of vehicular emissions, and surprisingly, also resulted in an overall increase in emissions. It’s found that there was a significant gain in the median concentration of gases that were measured from air samples as chemical tracers for vehicular emissions.

The analysis has been performed by researchers from the Ministry of Earth Sciences, India Meteorological Department (IMD), Indian Institute of Tropical Meteorology (IITM) and Indian Institute of Science, Education and Research (IISER), Mohali,

The median concentration of 13 out of the 16 gases measured were higher in morning hours (7 am to 8 am) and afternoon hours (1.30 pm to 2.30 pm) on days once the plot was implemented as against three random reference days before and after the fortnight-long odd-even effort.

Talking to India Science Wire, Dr Vinayak Sinha, a part of the research team from IISER, explained the greater concentration of gases was probably because of the fact that though there was a decline in the amount of cars, there was an increase in the number of other vehicles on the road: public transportation trucks, buses, two wheelers, three wheelers as also CNG-operated automobiles that were exempted from the strategy.

A study by the Council on Energy, Environment and Water (CEEW) had found that the daily average number of automobiles increased by 10 percent during the odd-even period in January 2016 compared to the previous week of December 2015. The increase was attributed mostly to a 17 percent boost in two-wheelers, 12 percent boost in three-wheelers, 22 percent rise in taxis and 138 percent increase in the number of private buses.

Additionally, a large number of private vehicle owners seemed to have opted to commute before in the afternoon and later in the evening, before and after the odd-even rule had been enforced (from 8 am to 8 pm) to avoid penalty.

The research says “the odd-even rule could have led to traffic decongestion during peak hours, which may certainly have profited commuters. However, it also has to be considered that improved traffic emissions during times of the evening once the dilution effect because of the atmospheric boundary layer is low (early morning before 8 am and at night after sunset) could result in high peak concentration vulnerability for several health-relevant carcinogenic VOCs (volatile organic chemicals) such as benzene”.

Dr Sinha said the research looked in the concentration of chemical tracers that were specific for automobile emissions and biomass emissions, unlike many other studies that investigated the effect of the odd-even rule on ambient concentrations of nitrogen oxides, sulphur dioxides, ozone and particulate matter (PM10 and PM2.5), that can be driven by multiple emissions sources.

The report indicated that in future, arrangements be made for deploying systems for online measurement of VOCs at multiple strategic websites and webcams at sampling sites to find a better image of the quantity and kind of vehicles passing by. This might help address current uncertainties with respect to quantitative source apportionment of air pollutants.