Transport accessibility is a key factor influencing regional integration, spatial equity, and the efficiency of public service provision. Traditional distance-based measures often fail to reflect the actual performance of transport systems, making travel-time-based approaches more suitable for regional accessibility assessment. This study aims to evaluate automobile transport accessibility in Sumy Oblast, Ukraine, through multi-level GIS-based isochrone modelling at both district and regional scales. The methodology is based on weighted graph analysis, where territorial community centres are represented as nodes and road connections as weighted edges corresponding to estimated travel times. Shortest travel times were calculated using Dijkstra's algorithm, while continuous accessibility surfaces and isochrone maps were generated through spatial interpolation. The entire analytical workflow was implemented using open-source GIS and Python-based tools, ensuring transparency and reproducibility. The results reveal substantial spatial disparities in transport accessibility across Sumy Oblast. District-level analysis demonstrates considerable differences in accessibility patterns associated with the geographical position of district centres, transport network configuration, and natural barriers. Regional-scale modelling identifies a pronounced centre–periphery gradient, with communities surrounding the regional centre exhibiting the highest accessibility, whereas northern border communities experience the longest travel times. The comparison of district and regional accessibility demonstrates that efficient connectivity within a district does not necessarily ensure favourable accessibility to the regional centre. The study confirms that GIS-based multi-level isochrone modelling provides a robust and transferable framework for identifying spatial inequalities in transport accessibility and supports evidence-based regional planning, infrastructure prioritisation, and territorial decision-making.
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