Research data supporting the publication "Deteriorating emissions of the current vehicle fleet are a major threat to air quality improvement"

This study examines the impact of ageing on real-world emissions of cars and vans, subset by Euro 6 subclasses and fuel type (petrol and diesel), using over 90,000 real-world measurements of NO, NO2, NOx, CO, PM, and HC pollutants via remote sensing technology. Across the full Euro 6 fleet, disaggregated by vehicle and fuel type, consistent real-world ageing trends are observed, including increasing NO, NOx, and PM emissions for all vehicle types, pronounced NO2 increases in diesel vehicles, and divergent behaviour in CO and HC emissions between petrol and diesel vehicles.

Analysis of covariance identifies vehicle age as the primary factor influencing emissions (η2 = 0.29–0.34, p < 0.0001), outweighing the effects of Euro subclass or engine capacity. Petrol cars exhibit relatively stable emissions performance over time, while diesel vans show steeper degradation in NOx and PM emissions compared to diesel cars. The similarity of deterioration slopes across Euro 6 subclasses, despite progressive tightening of test protocols, raises concern about the effectiveness of current emission durability requirements.