Thermal Comfort Path Planning Tool for Urban Mobility in Austin, Texas

Abstract: Extreme heat poses a growing challenge for active transportation in cities like Austin, Texas, where conventional weather reporting (e.g. a single air temperature measurement for the whole city) fails to capture the large microclimate variations that pedestrians and cyclists actually experience. We present a novel walking and biking route planner that selects paths based on thermal comfort using the Universal Thermal Climate Index (UTCI) (Jendritzky et al., 2012) rather than just distance or travel time. This system combines high-resolution thermal modeling with real-time route mapping. We generate city-scale UTCI maps using SOLWEIG-GPU (Solar and LongWave Environmental Irradiance Geometry), to account for urban features (buildings, trees, etc.) and weather conditions (Lindberg et al., 2008; Kamath et al., 2026). For any given origin and destination, our tool calculates the average UTCI along each possible route and recommends the 'coolest' route, i.e. the path with the lowest heat stress (often the most shaded or otherwise thermally comfortable), while still being reasonably direct. In a case study for Austin, this approach identifies routes that significantly reduce pedestrians' heat exposure (often recommending routes with a much larger proportion of shade). Such thermally-informed route planning has important public health implications: by helping people avoid dangerous heat hotspots and sun-exposed areas, it can reduce the risk of heat-related illness and make walking or biking a safer choice even on hot days. This paper describes the motivation, methodology, results, and implications of the thermal comfort path planner, emphasizing the role of shade and thermal comfort in urban mobility and heat mitigation.