Analysis of future changes in bridge utilization based on demographic trends and road classification

Abstract

This study organizes the future utilization potential of municipal bridges by integrating projected demographic trends and road classification. Using 500-meter mesh-based future population projection data, spatial changes in inhabited areas in Hokkaido were analyzed. Bridge locations were overlaid with population data in a GIS environment to identify bridges expected to have no surrounding population in future periods. Road data from OpenStreetMap were used to classify roads into arterial and residential categories based on their functional tags. By combining demographic conditions and road classification, bridges were evaluated in terms of both surrounding population and network role. The results indicate that the number of bridges with no surrounding population is expected to increase as overall population declines. A considerable portion of these bridges is located on residential roads, particularly in rural municipalities. The findings suggest that population decline in Hokkaido is accompanied by a spatial contraction of inhabited areas. Integrating demographic projections and road classification enables systematic identification of bridges that may experience reduced future utilization.