# Prediction of Pollutant Emissions in Various Cases in Road Transport
## 2 Materials and Methods  
In this section, the authors used COERT (Computer Programme to Calculate Emission from Road Traffic), a complex modeling software tool for the calculation of air pollutant emissions from road transport. The applied methodology followed the IPPC (Integrated Pollution Prevention and Control) [16] and the _EMEP (European Monitoring and Evaluation Programme) Guidebook 2019_[17] guidelines, as well as those in Ntziachristos [18], which are basic sets of guidance for GHG and air pollutant emissions inventories. Using the COERT model made it possible to estimate emissions following international and EU law requirements. Road transport emissions estimates were based on:  
* Fuel consumption;* Engine size;
* Number of vehicles per category;
* Vehicle weight;
* Emissions control technology;
* Mileage per vehicle class;
* Mileage per road class (urban, rural, and highway);
* Average speed per vehicle type and per road class;
* Monthly temperature (minimum and maximum);
* Fuel characteristics. The mathematical approach included in the COPERT software is classified as a \"Tier 3\" approach for quantitative emissions assessment. The applied Tier 3 (the most complex emissions estimation methodology) approach estimates road transport exhaust emissions as the sum of hot-start and cold-start emissions [18]. Both processes have specific emissions factors, which vary depending on the vehicles' type and fuel, driving situation (urban, rural, and highway), and the climatic conditions (average monthly temperature) [18]. The general equation for the Tier 3 methodology is presented below [18]:  
\[E_{Total}=E_{Hot}+E_{Cold} \tag{1}\]  
where  
\(E_{Total}\)--total emissions [g] of any pollutant for the spatial and temporal resolution of the application;  
\(E_{Hot}\)--emissions [g] during stabilized (hot) engine operation;  
\(E_{Cold}\)--emissions [g] during transient thermal engine operation (cold start). It should be emphasized that all of the emissions factors included in the COPERT model were determined based on laboratory testing under the WLTP driving cycle [19]. In this section, the authors investigated the impact of changes in fuel structure on the emission of CO\({}_{2}\), NO\({}_{\chi}\), and PM2.5 by passenger cars (PCs), light-duty vehicles (LDVs), heavy-duty vehicles (HDVs), buses (urban buses and coaches), and L-category vehicles (mopeds and motorcycles) for particular Euro standards, vehicle segments, and different fuel types (petrol--P, diesel oil--D, liquefied petroleum gas--LPG, compressed natural gas--CNG, and biofuels). It is worth emphasizing that the names of the categories used were consistent with the COPERT model. The COPERT software calculations were based on the input data used to compile the Polish national emissions inventory for 2020 [20]. The estimations were conducted based on the following basic assumptions:  
* Number of actual driving vehicles per vehicle category (PCs--18,587,297, LDVs--2,224,407, HDVs and buses 819,809, L-category vehicles--2,248,651), engine size or vehicle weight, emissions control technology, and Polish fuel mix consumed by vehicles in 2020 [21];
* Share by road class (urban, rural, and highway) (Figure 1);
* Vehicles' average velocities (Figure 2) [22];
* Maximum and minimum monthly temperature for Poland in 2020. The data are given below. The subject of analysis was related to the annual assessment of air emissions generated by the road transport sector on the regional (country) level. This kind of analysis is impossible to carry out as a laboratory experiment. However, the modeling software used [18] is based on laboratory testing of particular types of vehicles. In the Polish national inventory of pollutant and greenhouse gas emissions, the share of PC and LDV vehicles in urban traffic was over 35%, and in rural traffic it was about 50%. In cities, the average speed was about 30 km/h, and in extra-urban areas it was 70 and 65 km/h. Most HDVs and coaches traveled at an average velocity of 55 km/h in rural areas.