Emission measurements with ‘Plume chasing’ and subsequent inspection of heavy-duty vehicle (HDV) high emitters

The novel plume chasing technique creates an ‘on-road’ laboratory to measure real-world emissions, which can identify and then follow high-emitting vehicles on their journeys. The plume-chase vehicle was deployed mainly on highways across the North-East of Slovakia, collecting nearly 3,000 measurements in autumn 2023 and measured in real-time the nitrogen oxides (NO, NO₂) and particle (black carbon and particle number) emissions from the vehicles it followed.Schematic setup of a plume chaser installed in a vehicle measuring the exhaust emissions from the truck in front.

The report, produced by Airyx on behalf of the TRUE Initiative, analyzed the testing results and determined that 34% of the approximately 2,000 HDVs sampled were classified as showing suspicious or high NO_x emissions. The rate of suspicious or high emitters was significantly higher among older trucks certified to Euro IV and Euro V than those certified to Euro VI. This is likely because HDVs certified to Euro VI are still under warranty and therefore less likely to have defective or manipulated emission control systems.