Effects of Creating Street Greenery in Urban Pedestrian Roads on Microclimates and Particulate Matter Concentrations

Urbanization can increase artificial coverage rates and emissions by causing increases in traffic, which represents a serious health risk to pedestrians. To create pedestrian-friendly environments in urban canyons, this study examined their microclimates and air quality; methods to improve the pedestrian environment were also explored, based on the current street green space practices in Seoul, Korea. Under these current standards, the physiologically equivalent temperature (PET) of the pedestrian roads was predicted to decrease by 1.29–1.44 °C, but this was insufficient to adjust the thermal stress level. The air temperature of the pedestrian road declined slightly; fine dust concentrations increased, and ozone concentrations decreased. The effects of increasing the planting occupancy on the pedestrian environment were then simulated, which resulted in decreases in PET of 3.04–3.49 °C, depending on the floor area ratio, thereby effectively lowering the thermal stress stage. The particulate matter concentrations increased, however, and the air quality deteriorated. Therefore, street greenery planning alone cannot sufficiently improve both the microclimate and air quality of urban pedestrian roads. Thus, it is necessary to plan street greenery spaces in parallel with measures to improve air quality.