## 2 Materials and Methods
### Scenario Development  
To assess the effectiveness of different mitigation strategies in reducing air pollution and improving outdoor thermal comfort, two design scenarios were developed and simulated using the calibrated ENVI-met model. Both scenarios were compared to the current configuration of the university campus, which serves as the baseline scenario, with a focus on spatial variations in PM concentrations and thermal comfort indicators such as MRT and UTCI. The two scenarios were specifically designed to test the influence of traffic reduction as a key variable affecting environmental outcomes. Scenario 1 was conceived as a high-intensity traffic mitigation scenario, involving strong interventions to reduce vehicular circulation and assess the maximum achievable benefits through mobility-focused actions. Scenario 2, by contrast, was developed to explore whether a more moderate and politically feasible reduction in traffic could still deliver comparable environmental improvements if combined with more substantial material and vegetative interventions. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Thermal Sensation** & **UTCI (\({}^{\circ}\)C)** & **Physiological Stress** \\ \hline Very Hot & \(>\)46 & Extreme heat stress \\ Hot & 38–46 & Very strong heat stress \\ Warm & 32–38 & Strong heat stress \\ Slightly Warm & 26–32 & Moderate heat stress \\ Comfortable & 9–26 & No thermal stress \\ Slightly Cool & 0–9 & Slight cold stress \\ Cool & \(-\)13–0 & Moderate cold stress \\ Cold & \(-\)27—13 & Strong cold stress \\ Very Cold & \(-\)40—27 & Very strong cold stress \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Thermal sensations and different groups in UTCI. Importantly, both scenarios follow an integrated approach, combining mobility strategies with physical transformations of the urban space in order to assess potential synergies between traffic management and environmental design. Scenario 2, in particular, was also intended to evaluate whether solutions such as photocatalytic pavements, permeable surfaces, and increased greenery could partially compensate for the more limited traffic reduction while still ensuring measurable benefits in terms of air quality and thermal comfort. This structure reflects realistic urban planning practices where mobility constraints are moderate but supported by spatial and material innovation. Scenario 1 emphasizes a strong reduction in traffic volume (\(-50\%\)) through the introduction of mini-roundabouts, raised pedestrian crossings, and redesigned road layouts aimed at reducing vehicle speeds and promoting walkability. Green interventions are limited to the planting of small trees and shrubs at strategic locations such as building entrances and pedestrian paths. The spatial configuration of Scenario 1 is illustrated in Figure 5.  
Scenario 2, in contrast, applies a 30% traffic reduction and prioritizes enhanced environmental interventions, including a higher density of vegetation, the addition of medium-to-large canopy trees along major roads, the replacement of asphalt parking areas with permeable pavements, and the resurfacing of pedestrian paths with photocatalytic materials. These interventions are illustrated in Figure 6.  
A total of 6480 m\({}^{2}\) was renovated in Scenario 2: 2450 m\({}^{2}\) (37.8%) with draining pavements and 4030 m\({}^{2}\) (62.2%) with photocatalytic pavements, as summarized in Table 8. Materials were selected based on their thermal and optical properties, ensuring both functional performance and visual compatibility with the campus context. The Green Cover Ratio (GCR) in Scenario 2 increased to 10.2%, compared to 8.0% in the baseline and 8.8% in Scenario 1, corresponding to relative improvements of +26% and +15.5%, respectively. Vegetation types used in both scenarios include deciduous and coniferous trees, dense hedges, and grass cover, selected for their shading potential, physiological resilience, and suitability for Mediterranean climate conditions.