Detection of high-emitters: Variables affecting particle number emissions in Finnish vehicle fleet

• Data from 232 vehicles collected during PTI, representing the Finnish vehicle fleet. • PTI emission distribution based on Euro class for gasoline and diesel vehicles. • We assessed effects of vehicle parameters on emissions (highway, PTI) • Distribution of emissions for Finnish fleet were estimated. Periodical technical inspection (PTI) measurements are used for emission control in terms of PN, mainly to detect DPF malfunction. However, the real goal is to reduce PN driving emissions. In this study, we attempted to understand what properties of vehicles lead to high emissions in PTI and motorway driving. Two datasets were used: PTI dataset introduced in this study and chase dataset from earlier literature. The impact of vehicle parameters on emissions was modeled. Vehicle parameters, especially model year and engine size, had significant effect on average emissions of a vehicle. The effect of engine size was different for diesel and gasoline vehicles, highlighting the processes affecting the formation of PN emissions. As expected, the effect of high emitters on the total PN emissions were significant: 50 % of total emissions were produced by 10 % of vehicles in motorway driving and by under 5 % in PTI.