A UNIFIED TRAVEL-TIME ISOCHRONE METHODOLOGY FOR OPERATIONAL COVERAGE ANALYSIS: AN OPEN-DATA DEMONSTRATION FOR THE SILESIAN PROVINCE

Abstract

Operational coverage analysis (AZO) is a planning obligation of the State Fire Service that – following a law amendment – has been explicitly brought within the statutory delegation, with geographic information systems (GIS) increasingly expected in operational planning. Yet no unified methodology for delineating travel-time isochrones exists, so results produced by different command units are not comparable. This paper proposes a unified methodology based on the existing official planning parameters of the National Headquarters of the State Fire Service (turnout time of 3 min for professional and 10 min for volunteer units, and speeds of 75/60/50/30 km/h by road category), supplemented with elements that current regulations leave unregulated: an off-road access model, the construction of the coverage surface, and population-weighted demand-point measurement. Using open data for the Silesian Province – deliberately made open so that any differences areattributable to the method rather than to data access – the cost of non-standardisation was measured. With identical motion parameters, the choice of surface construction alone changes the populationcoverage indicator by 9.7 percentage points for the 15-min threshold (1,288 km of areas wrongly classified as covered); a decomposition shows that ignoring turnout time and using statutory speed limits add to this separately. The KSRG regulation in force since July 1, 2026 confirms a single 15-min arrival threshold but does not specify how the corresponding isochrones are to be delineated; the findings therefore justify anchoring a unified isochrone methodology in an amendment to thatregulation or in the National Headquarters’ guidelines.