Gaseous Emissions from Heavy-Duty Diesel Vehicles Across China V-VII Standards: Influences of Payload, Ambient Temperature, and Driving Dynamics

Heavy-duty diesel vehicles (HDDVs) are major sources of both gaseous pollutants and greenhouse gases in the atmosphere. However, a systematic evaluation of their multi-pollutant emission characteristics under complex operating conditions, particularly concerning the prospective China VII standards, remains insufficiently addressed. To bridge this gap, we tested a total of 14 HDDVs spanning China V, VI, and VII standards on a chassis dynamometer over standard driving cycles, evaluating effects of standard stringency, payload, engine condition, and ambient temperature on carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC), and nitrogen oxides (NOx) emissions. Results show that stricter emission standards significantly reduced NOx emission factors (EFs). China VII test vehicles exhibited substantially lower THC EFs than China V and VI test vehicles, while CO2 EFs remained comparable across three emission standards. Payload significantly affected THC and NOx EFs for the tested China VI HDDVs, but had no significant effect on CO2 emission. In addition, China VII HDDVs maintained low pollutant levels under all load conditions. Significant differences in NOx EFs between cold and hot starts were exclusively observed for China VII test vehicles. Furthermore, both CO and THC EFs exhibited a clear upward trend with decreasing ambient temperature. Speed-dependent analysis revealed distinct emission characteristics, with CO and NOx peaking at medium speeds, THC at high speeds, and all three closely tied to acceleration events. This work elucidates the coupled effects of multiple operational variables on real-world HDDV tailpipe emissions, thereby providing a robust basis for optimizing control technologies and informing emission policies.