Hanshin Expressway Public Corporation provides toll roads extending 200 km in the Osaka Kobe (Hanshin) area that are traveled by an average of over 900, 000 vehicles daily. Some of the toll roads were constructed almost thirty years ago and have started to suffer minor damage hem and there. To locate such damage, all the structures of Hanshin Expressway have been inspected every five to seven years, regardless of their time in service. The occurrence of damage varies widely depending on the design standards current when the structures were designed. This has prompted Hanshin Expressway to divide the routes into three groups mccording to the design standards appliod; and to inspect the groups every 4, 6 or 8 years. The intention is to maximize the structure inspection efficiency by differentiating the inspection periods according to the historical occurrence of damage, thus spreading the inspection effort and making best use of the inspection budget
