### Current State of Knowledge on Particulate Matter Emissions from Road Transport
\begin{table}
\begin{tabular}{c c} \hline \hline
**Sources of Particulate Matters or Their** & **Classification of Particulate Matters or Their** \\
**Emission Sources Classification** & **Emission Sources** \\ \hline \multirow{3}{*}{Classification of particulate matters for the needs of the inventory [7; 8; 29]} & total suspended particles (TSP); \\  & fine particles PM10 (PM10 particulate matter); \\  & free particles PM2.5 (PM2.5 particulate matter); \\  & soot (black carbon) \\ \cline{1-1}  & total emissions; \\ \cline{1-1}  & emissions from sources other than engine exhaust \\ \cline{1-1}  & than engine exhaust including PM emission \\ \cline{1-1}  & from vehicle tribological systems interacting \\ \cline{1-1}  & with the environment, mainly [5; 6; 7; 8; 21; 24; 29] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Different classifications of particulate matters and their emission sources. Figure 2 shows the numbers of vehicles in the cumulative categories that are the focus of this study. Figure 3 shows the average annual mileage of vehicles in each cumulative category. Figure 4 shows the average travel velocity of each cumulative category of vehicles under traffic conditions: urban (inside cities), rural (outside cities) and on highways. Figure 5 shows the share of the distance travelled by cumulative category vehicles under urban, rural and highway traffic conditions in the total distance travelled by these vehicles. Figure 3: Annual mileage (P) of passenger cars (PC), light duty vehicles (LDV), heavy duty vehicles (HDT), urban buses (UB), coaches (C), motorcycles and quads (Mc) and mopeds (Mp). Figure 2: Number (N) of passenger cars (PC), light duty vehicles (LDV), heavy duty vehicles (HDT), urban buses (UB), coaches (C), motorcycles and quads (Mc), mopeds (Mp) and all vehicles (V). The present study addresses the following key assessment criteria:  
* share of particle emissions in total particulate matter emissions;
* share of particle emissions and total particulate matter emissions from sources other than vehicle exhaust in particle emissions in total particulate matter emissions from all sources;
* influence of vehicle traffic models on specific fractions of particulate matter emissions and on total emissions of particulate matter inside and outside cities, as well as on highways. Figure 4: Average velocity (\(v_{AV}\)) of passenger cars (PC), light duty vehicles (LDV), heavy duty vehicles (HDT), urban buses (UB), coaches (C), motorcycles and quads (Mc) and mopeds (Mp) under different traffic conditions: urban (U), rural (R) and highway (H). Figure 5: Share of distance (u) in urban (U), rural (R) and highway (H) traffic conditions at all distances for passenger cars (PC), light duty vehicles (LDV), heavy duty vehicles (HDT), urban buses (UB), coaches (C), motorcycles and quads (Mc) and mopeds (Mp). Results on Environmental Hazards from Road Transport Particulate Matter Based on the Emission Inventory  
Figures 6-15 show an analysis of the particulate matter emissions from road transport. Figure 6 shows the national annual emissions of the studied fractions of particulate matter from road transport. The total particulate matter emissions from sources other than combustion engines was 62% of the total emissions. This indicates a high risk to the environment posed by particulate matter emissions from sources other than combustion engines, whereas technological developments in combustion engines have made it so their exhaust gases are no longer the main source of particulate matter leading to environmental harm. The highest relative annual emissions from the fractions examined in this study was for PM10 particles (78%), whereas for PM10 particles from sources other than exhaust gases this was 41%. The smallest was the relative annual emission of PM2.5 from sources other than exhaust gases (22%). Figure 7 shows the national annual emissions of total particulate matter from road transport as categorized by vehicle traffic pattern: urban, non-urban (rural), highway and all traffic conditions.