Road greening markedly impacts road thermal comfort and air quality. However, previous studies have primarily focused on thermal comfort or PM_2.5 individually, with relatively few addressing both aspects comprehensively, particularly in humid regions. This study combined field measurements and simulations. It employed physiological equivalent temperature (PET) and quantified the horizontal distribution of particulate matter 2.5 (PM_2.5). The research examines the effects of planting spacing, tree species, and tree–shrub combinations on pedestrian walkways in humid climates during both summer and winter. Using measured tree data and road PM_2.5, a plant model was established and pollution emission parameters were set to validate the effectiveness of the ENVI-met through fitting simulations under various scenarios. The results indicated that (1) plant spacing for trees influenced both the road thermal environment and PM_2.5 levels. Smaller spacing improved thermal conditions but increased PM_2.5. (2) trees with large canopies and high leaf area indices (LAIs) notably enhanced thermal comfort, while those with smaller canopies and dense understories facilitated PM_2.5 dispersion. The 3 m spacing resulted in a maximum absolute PM_2.5 concentration difference (C) of 5.05 μg/m³ in summer and a maximum mean absolute PM_2.5 concentration difference (M) in the downwind region of 2.13 μg/m³ in winter. (3) Combining trees with shrubs moderately improved pedestrian thermal comfort. However, taller shrubs elevated PM_2.5 concentrations on walkways; heights ranging from 1.5 m to 2 m in summer showed higher C values of 5.38 μg/m³ and 5.37 μg/m³. This study provides references and new perspectives for the optimization of roadway greening design in humid areas in China.

With the popularization of informal learning styles in universities, building overheads in hot and humid regions of China has become one of the main spaces for informal learning among college students in the region due to their improved thermal environmental conditions relative to outdoor spaces. However, the effects of thermal environmental changes on students’ learning performance on the overhead floors are not yet clear. Therefore, we recruited volunteers to conduct several tests, including the Stroop test, the Go/No-go test, the 2-back test, and the 3-back test, in the overhead space of a building in September and October. This was followed by a questionnaire survey, which yielded a total of 500 samples. Learning performance was quantified as a total of accuracy, response time, and final performance metrics. The results show that in hot and humid regions of China, the thermal perception of college students in the overhead was mainly related to Ta and Tmrt, and the relationship with Va was not significant; the maximum acceptable physiological equivalent temperature of college students in the overhead space was 30.3 °C; the change in the thermal environment had an effect on the learning performance of the four tests, and under neutral to slightly warm temperature (22.1–31.2 °C physiological equivalent temperature), the learning performance of the perceptually oriented and short-term memory task types increased by 2.5% and 1.1%, and the relationship between thermal environment and learning performance was not significant when the short-term memory task became more difficult. Attention-oriented learning had a relationship between the spatial thermal environment and learning performance in overhead spaces in hot and humid regions and suggests a basis for future overhead retrofitting.