Reimagining transport policy to check pollution

Delhi and the larger NCR must adopt a forward-looking, data-driven strategy to reduce transport emissions

- Anirudh Narla and Amit Bhatt

Every winter, the return of low wind speeds and temperature inversions in Delhi-National Capital Region (NCR) reignites the familiar debate on deteriorating air quality. From 2018 to 2024, Delhi recorded poor to severe air quality on the Air Quality Index (AQI) scale between October and February, every month except one. This winter is no exception. However, recent evidence suggests that Delhi’s air pollution crisis is no longer confined to the winter months.

Public and policy attention typically focuses on the high levels of particulate matter (PM) during winter. However, another key transport pollutant has been in the news lately: Nitrogen dioxide (NO2) levels in several areas of Delhi surged to three times the national safe limit and almost ten times the stricter World Health Organization (WHO) limit in November. A similar situation prevailed in the preceding years. According to the Union ministry of health and family welfare, higher NO2 levels in Delhi were associated with increased emergency visits to hospitals.

NO2 is part of a group of gases known as nitrogen oxides (NOx) which includes nitric oxide (NO), another major pollutant from vehicles. NO readily transforms into harmful NO2 in the air, and this NO2 also plays a key role in the formation of ground-level ozone — a secondary pollutant that is harmful to human health and the environment (unlike stratospheric ozone).