Remote sensing of motor vehicle emissions in Seoul
This study analyzes the real-world emissions data collected by remote sensing in Seoul in 2019. The testing campaign was conducted at 11 sites, and the in-use emissions of more than 740,000 vehicles were measured. The sampled fleet was mostly comprised of light-duty passenger vehicles, including cars and vans.
The analysis found that real-world NOx emissions from Grade 4 (Euro 4) diesel light-duty vehicles are comparable or even higher than Grade 5 (pre-Euro 4) diesel light-duty vehicles. Currently, Grade 5 vehicles are banned from entering the Green Transport Zone in Seoul to reduce emissions from vehicles used in the area and improve urban air quality. The analysis indicates that emissions from Grade 4 vehicles should be banned from the Green Transport Zone as well.
In addition, the analysis indicates that UV smoke from Grade 5 diesel light-duty vehicles retrofitted with a diesel particulate filter are 37% lower than those without, but this reduction is much lower than expected. Therefore, polices should be considered that encourage the retirement of the older vehicle fleet rather than retrofitting the vehicles with diesel particulate filter. By retiring Grade 5 diesel vehicles and expanding driving ban to include Grade 4 vehicles, UV smoke and NOx emissions from in-use diesel vehicles would be significantly reduced and would further improve the urban air quality in Seoul.