Real-World Heavy-Duty Truck Emissions: 5-km Road-Network Inventory Implications

Heavy-duty trucks (HDTs) are a major source of nitrogen oxides (NOₓ) and combustion-derived particulate matter along freight corridors and in rapidly urbanizing regions, yet Indian emission inventories often rely on emission factors (EFs) that are weakly constrained under real-world operation and insufficiently representative of fleet diversity. Here, we quantify real-world HDV EFs using the Versatile Source Sampling System (VS3) from in-use measurements spanning multiple Bharat Stage norms (BS III, BS IV, & BS VI), vehicle ages, gross vehicle weight classes (12–16, 16–30, 30–42 tons), axle configurations, and both diesel and CNG fuel. We observe systematic reductions in regulated pollutants with tightening standards. Compared with older-generation vehicles, the newest standards show ~85–90% lower PM_2.5, 90–95% lower CO, and 85–95% lower NOₓ under real-world conditions. For the combined diesel+CNG fleet, most PM₂₅ improvement occurs between the two earlier standards (roughly an 80% reduction), with comparatively smaller additional changes thereafter, whereas NOₓ exhibits modest early reductions followed by a pronounced step decrease (roughly 80–85%) with the newest standard. Within the latest standard, diesel vehicles remain higher-emitting than CNG, with diesel showing roughly ~65–75% higher PM₂.₅ and ~75–85% higher NOₓ on average under comparable operating regimes. Multivariate analysis indicates that emission standard and axle category (as a proxy for duty and operating regime) explain most EF variability.

Building on these measurement-constrained EFs, we develop a transparent and reproducible national HDTs emissions inventory workflow at 5-km spatial resolution, integrating state/UT fleet statistics, survival-function-based age-mix reconstruction, and road-network spatial allocation. The framework supports scenario analysis by contrasting literature-based baselines with updated measurement-informed EFs, producing gridded emissions suitable for chemical transport modeling, exposure assessment, and evaluation of corridor-focused control strategies.

Keywords: heavy-duty vehicles; real-world emissions; emission factors; VS3; Bharat Stage; NO_x; PM_2.5; diesel; CNG; road-network inventory; 5-km gridded emissions.