Emission inventory for road transport in India in 2020: framework and post facto policy impact assessment.

India's growing population and economic development lead to an increase in transport emissions. Quantification of emission at frequent intervals is required to assess the emission levels and impact of implemented control policies. Implemented policies affect the fleet configuration over time. Therefore, in the present paper, an age-wise emission analysis framework is developed for the road transport sector with updated fleet characteristics corresponding to the vehicles' age. The results show that fuel consumption is estimated to be 92 (87-95) Mt, and total CO2, CO, PM, and NOx vehicle emissions are estimated to be 274 (265-292) Tg, 4463 (3253-6676) Gg, 164 (119-250) Gg, and 2378 (2191-3045) Gg, respectively for the reference year 2020. The study contributes by developing an inventory for the fleet of 2020, which is used as a benchmark to compare past emission inventory, evaluate control policies, estimate state-wise vehicle emission inventories, and identify significant emitters in the fleet. Sensitivity analysis indicates the considerable variation in total emissions resulting from different age-mix of vehicles. Among the investigated policies, advancement in emission norms followed by fuel efficiency improvement in vehicles led to a substantial reduction in gaseous pollutants. Based on the inventory results, suitable policies are suggested for India's future fleet, and the need for country-level fleet characteristics data is recommended.