Developed within the framework of the MOST (Sustainable Mobility Centre) research project, this paper explores the potential of secondary railway stations as strategic nodes for promoting active and sustainable mobility within the 15-min city paradigm. Focusing on the Roma Val d’Ala station, a representative case in the northeastern metropolitan area of Rome, the study develops and applies a GIS-based methodology to assess local accessibility conditions. Two Key Performance Indicators (KPIs) are proposed—Intermodality and Service Proximity—designed to measure the spatial distribution and diversity of transport nodes and essential urban services within a walkable and cyclable catchment area. The method combines network-based isochrones, spatial buffers, and hexagonal grid analysis, and integrates multiple datasets including institutional geoportals, commercial POI providers, and community-contributed data. The application to Roma Val d’Ala highlights both accessibility gaps and opportunities for spatial and functional regeneration. The station, situated in a largely residential area is also part of a broader infrastructural plan for the closure of the Rome Railway Belt, which may enhance its strategic role. The results demonstrate how the proposed methodology can support spatial analysis and guide interventions for urban regeneration and sustainable mobility. The framework is replicable and scalable, offering a decision-support tool to identify and prioritise active mobility improvements across a wider network of secondary stations.