Climate-Responsive First/Last-Mile Accessibility Around Riyadh Metro: A Multi-Scalar Decision-Support Framework for Smart Urban Mobility

First/last-mile accessibility around metro stations in hot–arid cities depends not only on proximity and network connectivity but also on climatic exposure, physical movement friction, visual legibility, and route continuity. This study develops and tests a multi-scalar spatial decision-support framework for evaluating and retrofitting a station-parallel pedestrian corridor along the Riyadh Metro. The framework integrates five registered diagnostic dimensions—shade continuity, relative solar exposure, physical route friction, visual route confirmation, and inferred movement correspondence—followed by a separate comparison of conceptual retrofit options. Twelve route segments were assessed under baseline conditions and three retrofit scenarios: tree planting, lightweight canopies, and a hybrid strategy. The baseline analysis indicated 18% modeled shade continuity, a relative solar-exposure index (CSEI) of 4.2, approximately 42% availability of route-confirmation cues, and four segments in the highest study-defined IPS screening band. Under the hybrid established-canopy design state, the corresponding modeled values were 84%, 2.1%, and 75%, while spatial support for inferred origin–destination relationships increased from approximately 67% to 92%. The hybrid ranked highest within the principal uncosted comparison. These results indicate comparative spatial performance rather than measured thermal relief, successful wayfinding, observed pedestrian movement, or verified accessibility. The framework supports preliminary retrofit screening, subject to environmental, behavioral, accessibility, and cross-typology validation.