On-road vehicle emissions measurements show a significant reduction in black carbon and nitrogen oxide emissions in Euro 6c and 6d diesel-powered cars

Abstract. Real-world vehicle emissions measurement methods were developed to bridge the gap between laboratory tests and actual on-road emissions, including the variability in vehicles, drivers, and environmental conditions. The on-road chasing method is a cost-effective approach capable of capturing emissions from numerous vehicles. While it has been used extensively to measure truck emissions, it has not been applied systematically to diesel- and gasoline-powered cars. This study addresses that gap by comparing data from three on-road chasing campaigns conducted in 2011, 2017, and 2023 to evaluate the impact of emissions control technologies and regulatory policies on diesel- and gasoline-powered vehicles. Results show that diesel particulate filters (DPFs) reduce black carbon (BC) emission factors by 88 % compared to pre-DPF Euro 4 diesel-powered cars, while real driving emissions (RDE) regulations lower nitrogen oxide (NOx) emissions by 86 % relative to pre-RDE Euro 6b diesel-powered cars. This is the first study to apply the chasing method over a decade to a representative sample of European vehicles and to report real-world BC emission factors for cars compliant with Euro 5b–6d. Lorentz curve analysis reveals a growing influence of high-emission vehicles (“super-emitters”) on total fleet emissions, suggesting that targeting super-emitters could yield substantial reductions in traffic-related pollution. Despite methodological variability, the results are consistent across campaigns and align with major regulatory milestones, thus confirming the chasing method's utility as a robust tool for super-emitter identification and fleet-wide emissions monitoring. By providing real-world evidence of regulatory effectiveness, this work supports scientific understanding and confidence in emissions policy.