Personal Environmental Exposure Digital Twin Icarus 25 Framework

Icarus is an open-source urban digital twin that links a full metropolitan activity-based travel model with high-resolution environmental data to measure and minimize personal heat exposure. By embedding sub-meter, hourly Mean Radiant Temperature (TMRT) rasters into a multimodal street network, the framework both captures how individuals accumulate exposure during their daily travel, as well as is capable of rerouting them to cooler alternative paths. Earlier applications showed that TMRT-weighted routing can cool up to ten times more trips than infrastructure retrofits alone, positioning Icarus as a decision-support tool for planners, public-health officials and researchers concerned with climate equity. Significant improvements to the earlier version of the Icarus framework are documented in this report. In addition to incorporating multiple hazards with the objective of minimizing each, this new framework also accounts for changing hazard conditions as people complete their trips, combining improved data resolution with more adaptive routing methods. Key upgrades also include a time-dependent routing engine that accounts for shifting hazard patterns during each trip and finer spatial precision through edge-splitting at trip endpoints. The framework adds sub-edge temperature sampling and localized network indexing, greatly improving both accuracy and computational efficiency. Together, these developments turn Icarus 25 into a dynamic, multi-hazard digital twin that can measure and minimize personal exposure across millions of walking and biking trips while remaining deployable for large-scale urban analyses.