Delhi’s Truck Pollution: Regional Freight, Not Transit, Main Culprit, Study Finds

A joint study by the Air Pollution Action Group (A-PAG), IIT Delhi, and The Energy and Resources Institute (TERI) has revealed that Delhi’s truck pollution problem is driven primarily by regional freight traffic rather than long-distance transit vehicles.

The report, released on Monday, shows that 92% of heavy-duty trucks entering Delhi list the Capital as their final destination, with only 8% being “bypass” or transit traffic. The vast majority of these trucks originate from and are destined for states within the National Capital Region (NCR).

“The majority of trucks entering Delhi originate from and return to NCR States, meaning Delhi alone cannot solve this problem,” said Anju Goel, associate director at TERI. “The strategies identified in this report — from Low Emission Zone (LEZ) implementation to electric vehicle fleet transition — require coordinated action across the NCR. Policymakers at both the Central and State levels need to align on a common, data-backed road map.”

The findings align with the latest assessment by the Commission for Air Quality Management (CAQM), which identifies transport as the largest local source of Delhi’s PM2.5 pollution, contributing about 23%. Other major sources include secondary particulate formation and dust. While crop residue burning worsens pollution during winter, the year-round air quality burden is driven largely by local sources such as transport, industry, dust, and residential fuel use.

The study estimates that around 16,900 heavy-duty trucks enter Delhi every day, making freight a disproportionately large source of transport-related pollution. Inter-State trucks account for 23% of Delhi’s transport sector PM2.5 emissions, but their contribution rises sharply to 61% at night and early morning, when nearly three-quarters of truck traffic enters the city. These trucks emit approximately 52 kg of PM2.5, three tonnes of nitrogen oxides (NOx), and 2.5 tonnes of carbon monoxide daily.

The report questions two policy approaches that have dominated recent discussions. First, it argues against phasing out vehicles based solely on age, recommending instead direct measurement of particulate matter and NOx emissions through expanded automated testing stations and on-board diagnostics. Second, it is skeptical of retrofitting older trucks with diesel particulate filters and NOx control devices, citing unresolved issues related to cost, certification, standards, long-term reliability, and large-scale implementation.

The study recommends a package of complementary measures to reduce emissions while improving freight efficiency. Individual interventions could deliver significant reductions in freight-related PM2.5 emissions: 21% through optimising empty backhauls, 23% through urban freight consolidation, and up to 51% by barring pre-BS-VI trucks. However, the researchers caution that these benefits overlap and cannot be simply added together. Notably, 51% of trucks leave Delhi empty after deliveries, so reducing empty return trips could be a key air quality intervention.