###### Abstract  
Urban campuses face critical environmental challenges due to high pedestrian density, traffic-induced air pollution, and thermal stress, especially in compact Mediterranean settings. These conditions can compromise the usability and livability of outdoor spaces. This study investigates whether greening and material-based interventions can offset a lower degree of traffic reduction in improving air quality and thermal comfort. The University Campus of Catania (Southern Italy) served as the case study. An integrated microscale simulation framework using ENVI-met was developed, calibrated, and validated with local traffic, meteorological data, and field measurements of PM\({}_{10}\) and PM\({}_{2.5}\). Three scenarios were tested: a baseline, Scenario 1 (50% traffic reduction with moderate greening), and Scenario 2 (30% traffic reduction with more extensive greening and material interventions). Results showed that Scenario 1 consistently outperformed Scenario 2 in all pedestrian hotspots. The highest reductions recorded in Scenario 1 were \(-0.150\)\(\upmu\)g/m\({}^{3}\) for PM\({}_{2.5}\) (\(-11.5\%\)), \(-0.069\)\(\upmu\)g/m\({}^{3}\) for PM\({}_{10}\) (\(-5.9\%\)), \(-2.16\)\(\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  
challenges, urban air pollution and the urban heat island (UHI) effect stand out as key issues with serious implications for public health and climate resilience. The replacement of vegetated surfaces with impermeable, low-reflectance materials such as asphalt and concrete plays a major role in these phenomena, as such materials absorb and re-emit solar radiation, increasing ambient temperatures and energy demand [2; 3]. At the same time, motorized traffic remains one of the main sources of urban air pollution, emitting a complex mix of pollutants--including carbon monoxide (CO), nitrogen and sulfur oxides (NO\({}_{\rm x}\), SO\({}_{\rm x}\)), particulate matter (PM\({}_{2.5}\), PM\({}_{10}\)), volatile organic compounds (VOC\({}_{\rm s}\)), and ozone (O\({}_{3}\))--all of which are strongly associated with elevated risks of asthma, bronchitis, and cardiovascular diseases [4; 5; 6; 7; 8; 9; 10; 11; 12]. In response to these well-documented health impacts, several international and regional institutions have established air quality standards to define acceptable exposure levels. The 2021 guidelines of the World Health Organization (WHO) recommend a 24 h mean limit of 15 \(\upmu\)g/m\({}^{3}\) for PM\({}_{2.5}\) and 45 \(\upmu\)g/m\({}^{3}\) for PM\({}_{10}\), while the European Union's Directive 2008/50/EC sets an annual mean of 25 \(\upmu\)g/m\({}^{3}\) for PM\({}_{2.5}\) and a 24 h mean of 50 \(\upmu\)g/m\({}^{3}\) for PM\({}_{10}\), not to be exceeded more than 35 times per year [13; 14]. These regulatory thresholds are not only intended to protect public health but also serve as references for urban environmental assessments and the design of effective mitigation strategies. Numerous studies have highlighted the potential of green infrastructure and innovative technologies to reduce air pollutants and thermal accumulation. Tree-lined streets, vegetative canopies, and photocatalytic surfaces with titanium dioxide can absorb or degrade NO\({}_{\rm x}\) and PM while also offering thermal benefits through shading and evapotranspiration [15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. However, their effectiveness depends on factors such as climate, urban form, and plant physiology. High temperatures can limit stomatal uptake by inducing closure [27], while cooler microclimates may reduce ozone formation via atmospheric chemical processes [28]. Urban traffic modeling has emerged as a key tool for estimating pollutant emissions under real-world conditions and supporting urban planning decisions. Advanced simulation platforms such as SUMO and VISSIM are increasingly integrated with Computational Fluid Dynamics (CFD) approaches to represent the complex dispersion behavior of pollutants in built environments [29; 30].