High Particle Number Emissions Determined with Robust Regression Plume Analysis (RRPA) from Hundreds of Vehicle Chases

Particle number emission factors were determined forhundreds ofindividual diesel and gasoline vehicles in their real operation onFinnish highways and regional roads in 2020 with one-by-one chasemeasurements and Robust Regression Plume Analysis (RRPA). RRPA isa rapid way to analyze data from a large number of vehicle chasesautomatically. The particle number emission factors were determinedfor four ranges of particle diameters (>1.3, > 2.5, > 10,and >23nm). The emission factors for most of the measured vehicles were observedto significantly exceed the non-volatile particle number limits usedin the most recent European emission regulation levels, for both light-dutyand heavy-duty vehicles. Additionally, most of the newest vehicles(covering regulation levels up to Euro 6), for which the particlenumber emission regulations (non-volatile >23 nm particles) apply,showed emission factors of the >23 nm particles clearly above theregulation limits. Although the experiments included measurementsof real-world plume particles (mixture of non-volatile and semi-volatileparticles) and not only the non-volatile regulated particles, it isimportant to note that the emissions of regulated particles were alsoestimated to exceed the limits, based on non-volatile >23 nm particlefraction from curbside studies. Moreover, the emission factors ofthe >1.3 nm particles were mostly about an order of magnitude highercompared to the >23 nm particles. Particle numberemission factors of hundreds of individualvehicles measured in their real operation exceed the particle numberlimits in European emission regulations by orders of magnitude.

Automated summary

Particle number emission factors were determined for hundreds of individual diesel and gasoline vehicles in their real operation. The emission factors for most vehicles exceeded the non-volatile particle number limits in European emission regulations. New vehicles, even those meeting the latest regulations, showed emission factors above the regulation limits. The emission factors of smaller particles were generally much higher compared to larger particles.