High emitting Slovakian trucks identified in new plume testing method
In Slovakia, the first-ever TRUE plume-chasing campaign testing system has successfully identified 34% Heavy-Duty Vehicles (HDVs) showing suspicious or high NOx emissions while driving on the roads.
The novel 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.
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 NOx 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
Roadside inspections were conducted alongside Slovak authorities during certain testing days to investigate the reasons for high emission rates. Of the 28 high or suspicious emitting HDVs inspected by police, no vehicle was wrongly classified as a high-emitter. Whether it was a defective emission reduction system, manipulation, or software issues, 96% of the sample had an emission error requiring attention, and when excluding suspicious emitters, 100% of the high emitters were proven to have one of these issues.
This study showcases the potential for a plume-chasing measurement system to support authorities in identifying vehicles with defective and/or manipulated emission control systems, which was proven efficient in a similar plume chasing campaign conducted in Prague in 2022 coordinated by TRUE partner ICCT, under the CARES project. A major advantage of this method over existing vehicle inspection methods is that plume chasing is completely contactless and undetectable by the vehicle which is being measured. The study highlights the potential for passive surveillance of high emitting vehicles if the equipment is installed within police or traffic inspection cars already driving on the roads.
Furthermore, measuring particulate numbers offers a unique way to assess the performance of diesel particulate filters (DPFs) in real-world conditions. The ‘on-road laboratory’ setup could detect diesel vehicles with high particulate emissions, enabling identification of vehicles with potentially defective or manipulated DPFs in real time, if combined with vehicle inspection.
The TRUE Initiative is expanding the use of this novel methodology across the globe with another plume chasing measurement campaign in Uganda’s capital city of Kampala. This project marks the first on-road vehicle emissions testing of its kind in Africa and aims to provide evidence to policymakers on the urgency to improve air quality in the rapidly growing metropolis.
Sheila Watson, FIA Foundation Deputy Director, said: “This report shows how this plume-chasing technique could be an exciting new addition to TRUE’s real-world emission testing and analysis work. In particular it enables the identification of specific individual vehicle issues of malfunction and tampering within a fleet which disproportionately impact air quality and public health, which will support those seeking to address them.”
Read the report ‘Emission measurements with “Plume chasing” and subsequent inspection of Heavy Duty Vehicle (HDV) high emitters’ here.
