Heavy-Duty Diesel Trucks on Highways in Beijing-Tianjin-Hebei: Constant Challenge in Pollution Control

Heavy-duty diesel trucks (HDDTs) contributed significantly to on-road air pollution. This study measured the traffic flow of HDDTs on seven national highways in Beijing-Tianjin-Hebei (BTH) region to estimate air pollutants of HDDTs from 2016 to 2020. The emission factors are corrected by the International Vehicle Emissions (IVE) model, traffic flow, and road length. Compared with 2016, traffic flow in 2019 increased by 41%, carbon monoxide (CO) and nitrogen oxide (NOx) emissions increased by 0.3% and 4%, while hydrocarbons (HC) and particulate matter (PM) emissions decreased by about 26% and 18%. The COVID-19 lockdowns did not cause significant annual changes in traffic flow and pollution emissions in 2020 compared with 2019, but there were substantial monthly variations in pollutant emissions. Our study showed that although control measures were implemented during the "Thirteenth Five-Year Plan" period, the substantial increase in regional HDDT transport posed a continuing challenge in reducing road traffic emissions.