On-road Evaluation of Emission Control in China V-VI Heavy-duty Diesel Trucks

This study evaluates the real-world emission impacts associated with the transition from China V to China VI standards for heavy-duty diesel trucks (HDDTs). On-road measurements from 24 HDDTs were obtained using Portable Emission Measurement Systems to quantify particle number (PN) and nitrogen oxides (NOx) emission factors (EFs) under diverse operating conditions. Comparisons were conducted among China V, China VI compliant, and China VI non-compliant vehicles, alongside an assessment of selective catalytic reduction (SCR) and exhaust gas recirculation (EGR) system performance. Fleet-level results indicate that the average PN and NOx EFs of China VI HDDTs were 5.48 and 0.75 times those of China V vehicles, primarily due to a substantial share of non-compliant trucks exceeding regulatory limits. Non-compliant HDDTs exhibited increases of 1,695.6% in PN and 85.6% in NOx EFs relative to China V, whereas compliant vehicles achieved reductions of 51.5% and 59.6%, respectively. Operating mode-specific analysis revealed inadequate PN control at low-to-medium speeds and NOx exceedances under high vehicle-specific power. SCR systems reduced NOx by 76.6-96.8%, with performance varying by compliance and operating mode, while EGR consistently lowered NOx emissions. These findings highlight the necessity for strengthened in-use compliance monitoring and enforcement under China VI regulations.