In the United States, many people have suffered losses caused by the collapse of deteriorated road bridges and subsequent road closures, and in Japan, bridges built during rapid economic growth are now reaching the end of their planned service period. Under these circumstances, instead of corrective maintenance, regular visual inspections of the bridges are performed once every five years to implement preventative maintenance. In this study, to identify those bridges prone to rapid

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... , deterioration rates were calculated based on data from two cycles of inspection results, and the environmental factors that impacted these rates were statistically analyzed based on Hayashi's quantification theory type I. The results clearly show that the bridge deterioration rate is significantly impacted by its specifications (superstructure materials, bridge length, year of construction), but that environmental factors also exert an equivalent impact. Therefore, considering environmental factors that can influence deterioration is expected to aid the development of more efficient and effective bridge maintenance plans.