Urban Proximity Under Andean Constraints: Spatial Inequalities in 15-Minute Pedestrian Accessibility to Primary Activity Nodes in Armenia, Colombia

This research examines pedestrian accessibility to primary urban activities in an intermediate Andean city where topography and uneven land-use distribution condition proximity. The study operationalizes the 15-min. city framework through a spatial assessment of walking access to nodes associated with education, health, recreation, commerce, and the mobility system. Using QGIS and OpenRouteService (ORS), 15-min. walking isochrones were generated from 164 centroids corresponding to normative urban sectors. These isochrones were intersected with georeferenced facility layers to compute Z(x), a cumulative-opportunity indicator representing the number of reachable nodes by category. Ordinary Kriging, was then used to transform discrete centroid-based measurements into continuous accessibility surfaces. Spatial dependence was evaluated through Moran’s I, and model performance was assessed by cross-validation statistics. The results reveal a marked center–periphery gradient across all activity categories. Education and recreation show broader medium-accessibility zones and weaker polynuclear patterns, whereas health and commerce display highly concentrated structures and extensive accessibility deficits. Low-accessibility areas reach 87.1% for health and 87.7% for commerce. The mobility system presents an intermediate condition, with 48.1% of the urban area still classified as low accessibility. These findings demonstrate tha t urban proximity is not a homogeneous citywide attribute, but a service-specific condition shaped by functional centrality, spatial inequality, and pedestrian-network constraints. The proposed method provides operational evidence for prioritizing urban planning interventions aimed at redistributing essential services and strengthening equitable walkable access.