A Novel Methodology for Evaluating Urban Surface Overheating and Its Impact on Pedestrians' Radiative Heat Exposure using Infrared Thermography

Climate change has raised outdoor surface temperatures, increasing pedestrians' vulnerability to heat stress. In this context, there is a lack of a methodology that captures the effects of directional radiation from urban environments on the human body, considering the relative positioning of pedestrians and surfaces. This paper proposes a methodology to evaluate the effects of surface temperatures on urban microclimate and pedestrian thermal comfort using infrared thermography. A 3D model of the urban environment was generated with projected thermographic images, also including a human body model to calculate view factors between each body segment and the surrounding surfaces. These view factors, combined with the surrounding temperatures, allow the determination of radiative heat flux from urban surfaces to each body part. The methodology was applied to three scenarios in Pisa using an AVIO TVS-600 thermal camera (320 × 240 pixels, IFOV 1.4 mrad, resolution 0.15°C): an open field, an urban canyon, and a semi-open area. Temperatures ranged from 15.0°C to 54.6°C, with longwave radiation fluxes to pedestrians varying due to view factors and solar radiation exposure of surfaces, peaking at around 500 W/m², especially those impacting the head section. The results are valuable for mapping longwave radiation and assessing pedestrian exposure to improve urban planning. They are also useful to evaluate the impact of longwave radiation on thermal comfort, analysing radiant asymmetries and variations in thermal perception across different body parts. Future studies should apply this methodology to enhance urban planning by addressing pedestrian thermal stress, including measurement campaigns with participants.