Development of Vehicular Emission Inventory using Traffic-Type-Road Classification: A Case Study of Nashik, India

Abstract

Vehicular emissions are a major contributor to deteriorating urban air quality; conventional bottom-up emission inventories apply a uniform citywide average Vehicle Kilometre Travelled (VKT) derived from limited manual counts. This oversimplification overlooks the heterogeneous composition of traffic and diurnal activity, leading to inflated and poorly resolved emission estimates. This study estimates a traffic-type-based road categorisation framework to generate link-specific VKT and quantify vehicular emissions for Nashik city, India. Classified vehicle count, dominant traffic category, road hierarchy and hourly activity duration were integrated across a 24-hour cycle, and emissions of PM, NOx, CO and HC were estimated using category-specific emission factors. Relative to the uniform VKT method, the proposed framework estimated 69% lower PM, 63% lower NOx, 53% lower CO and 55% lower HC and a more realistic emission load. Temporal assessment revealed that two-wheelers dominated daytime (internal road activity), contributing 63.1% of CO and 46.6% of HC, while Light-Duty Vehicles (LDV) and Heavy-Duty Vehicles (HDV) dominated the early hours, contributing 45.4% of NOx and 29% of PM. Unlike the conventional methods that yielded consistent patterns, the proposed emission inventory method highlighted spatial output with distinct emission hotspots along the freight corridors. The novelty of this methodology lies in traffic-type-based estimation of vehicle kilometre travelled, enabling explicit quantification of intra-urban and diurnal heterogeneity. This framework offers practicability for urban local bodies, transport planners and pollution regulatory authorities by providing an adaptable, data-efficient and policy-relevant methodology for air pollution control, emission hotspots identification, and city traffic management in rapidly motorising Indian cities.