15-minute protection as an applied 15-minute city indicator: A data‑driven metric and scenario engine for protective accessibility in Kharkiv

Conventional 15 min city (15MC) metrics focus on everyday amenity access and are not designed for minute-scale threats. We introduce 15 min protection (15MP) as an applied extension of 15MC: a network-based indicator of pedestrian reachability to shelters. Using Kharkiv, Ukraine, as a case study, we develop a scenario engine that maps walking isochrones to shelters across three states: pre-invasion, full-scale invasion with a power supplied, and “blackout”. The analysis integrates municipal shelter inventories, open street networks, and Transport Analysis Zones (TAZs). We propose the Protective Accessibility Progression Classification (PAPrC), a four-class typology that assigns each TAZ an auditable state based on the share of its area within a 15 min pedestrian isochrone to a structurally adequate shelter. This enables city planners and SUMP monitors to diagnose territorial adequacy and track progress toward protective accessibility goals. By aligning PAPrC (A-D Classes) with Sustainable Urban Mobility Plan (SUMP) indicators, we demonstrate how 15MP can inform resilience-oriented planning, translating proximity from a livability metric into a life-safety standard. The approach provides a reproducible, open-data workflow for other cities seeking to integrate protective accessibility into proximity-based planning under crisis conditions.