Particle number emission factors were determined for
hundreds of
individual diesel and gasoline vehicles in their real operation on
Finnish highways and regional roads in 2020 with one-by-one chase
measurements and Robust Regression Plume Analysis (RRPA). RRPA is
a rapid way to analyze data from a large number of vehicle chases
automatically. The particle number emission factors were determined
for four ranges of particle diameters (>1.3, > 2.5, > 10,
and >23
nm). The emission factors for most of the measured vehicles were observed
to significantly exceed the non-volatile particle number limits used
in the most recent European emission regulation levels, for both light-duty
and heavy-duty vehicles. Additionally, most of the newest vehicles
(covering regulation levels up to Euro 6), for which the particle
number emission regulations (non-volatile >23 nm particles) apply,
showed emission factors of the >23 nm particles clearly above the
regulation limits. Although the experiments included measurements
of real-world plume particles (mixture of non-volatile and semi-volatile
particles) and not only the non-volatile regulated particles, it is
important to note that the emissions of regulated particles were also
estimated to exceed the limits, based on non-volatile >23 nm particle
fraction from curbside studies. Moreover, the emission factors of
the >1.3 nm particles were mostly about an order of magnitude higher
compared to the >23 nm particles.