Universal Thermal Climate Index (UTCI)-adjusted pedestrian accessibility: Urban design exploration for climate-resilience in tropical climates

In dense cities, the urban heat island effect and thermal heat stress are exacerbated by the prevalence of impermeable surfaces and heat-trapping urban morphologies with repercussions including increased mortality rates. Assessing which urban design strategies best mitigate pedestrian heat stress is complex, with many contributing factors. To support computational performance-based planning approaches to heat resilient urban design, this study introduces the novel metric, UTCI-adjusted reach, measuring the number of destinations a pedestrian can reach using a heat-stress adjusted walking distance. This metric underlies the definition of the Reachable Urban Cool Spots (RUCS) method: a globally comparable and computationally efficient approach for evaluating pedestrian heat vulnerability within a masterplan. The RUCS method was tested for 32 masterplans generated for a case study site (112 ha) and explored across five design parameters, a sensitivity analysis further clarified the impact of 3 contextual assessment parameters on its results. Across the 32 masterplans, the RUCS score ranged from 0.08% to 18.0% for a single-hour simulation. Multi-day, multi hour simulations for selected masterplans established the diurnal thermal variability of the RUCS score. The introduced methods were shown to effectively synthesize multiple environmental predictions and urban network analyses and to support evidence-based computational design exploration to enhance the walkability of heat-vulnerable cities. RUCS will support planners and health professionals to assess existing districts, and designers to create walkable heat-resilient neighborhoods in the context of a warming climate.