## 2 Materials and Methods
### Simulation Framework  
The simulation framework integrates traffic emission modeling, pollutant dispersion, and outdoor thermal comfort evaluation within a unified and coherent microscale approach, implemented using the ENVI-met software. This holistic method allows for the simultaneous assessment of environmental variables that are usually treated separately, offering a more comprehensive view of the interactions between mobility patterns, atmospheric conditions, and built form. Traffic data collected from the extensive monitoring campaign were used to calculate the emission rates of PM\({}_{10}\) and PM\({}_{2.5}\), applying vehicle-specific emission factors obtained from internationally recognized databases, such as COPERT and the EMEP/EEA Guidebook. These emissions were input into ENVI-met using the \"Sources\" module, where urban roads were represented as linear stationary emitters positioned at a standardized height of 0.3 m, reflecting the average exhaust outlet of light-duty vehicles. Each emission line was defined by three key parameters: hourly traffic flow, the proportional composition of the local vehicle fleet, and the corresponding emission intensity (expressed in \(\upmu\)g/m\({}^{2}\)/s). Pollutant dispersion was simulated through the CFD-based module integrated into ENVI-met, which employs a high-resolution Eulerian approach to solve the advection-diffusion equation under complex urban boundary conditions. The model incorporates several physical processes that influence the behavior of airborne particles, including advection driven by prevailing winds, gravitational settling, and dry deposition on both artificial and vegetated surfaces. Particular attention is given to the role of urban morphology, as elements such as tall buildings, narrow street canyons, and open courtyards can generate turbulence, channeling, or stagnation zones that influence pollutant accumulation and dispersion patterns. These geometric characteristics were incorporated into the simulation domain using detailed 3D representations of the study area. To evaluate thermal comfort, ENVI-met computed the Mean Radiant Temperature (MRT) and the Universal Thermal Climate Index (UTCI) at high spatial and temporal resolutions. MRT quantifies the overall radiative load on the human body by integrating the effects of shortwave and longwave radiation from buildings, vegetation, and the sky dome. The model uses the formulation from VDI 3787 [69], combining [PERSON]'s \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Name** & **Leaf Type** & **Height (m)** & **LAD** & \begin{tabular}{l} **Albedo** \\ **\(\rho\) (-)** \\ \end{tabular} & \
\begin{tabular}{l} **Transmissivity** \\ **\(\tau\) (-)** \\ \end{tabular} &
\begin{tabular}{l} **Emissivity** \\ **(\(\varepsilon\))** \\ \end{tabular} \\ \hline Grass dense & - & 0.25 & 0.30 & 0.20 & 0.30 & 0.97 \\ Hedge light & Deciduous & 2.00 & 0.55 & 0.20 & 0.30 & 0.97 \\ Hedge dense & Deciduous & 1.00 & 1.00 & 0.20 & 0.30 & 0.97 \\ Hedge dense & Deciduous & 4.00 & 1.00 & 0.20 & 0.30 & 0.97 \\ Tree conic, small trunk, dense, large & Conifer & 25.00 & 1.00 & 0.12 & 0.10 & 0.96 \\ Tree, cylindric, large & Conifer & 25.00 & 1.50 & 0.12 & 0.10 & 0.96 \\ Tree spherical, medium & Deciduous & 15.00 & 1.00 & 0.18 & 0.30 & 0.96 \\ trunk, dense, medium & Conifer & 15.00 & 1.00 & 0.12 & 0.10 & 0.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Thermo-physical and optical properties of plants included in the model. law, directional view factors, and fixed coefficients for emissivity (\(\epsilon_{\rm p}\) = 0.97) and shortwave absorption (\(\alpha_{\rm p}\) = 0.7) [70; 71; 72; 73]. Recent studies have shown that Mean Radiant Temperature (MRT) plays a central role in determining outdoor thermal comfort, especially in highly urbanized and sun-exposed environments.