Assessment methodologies for Italian existing bridges are investigated considering national technical recommendations (NTC2018 and MIT2022) as well as pertinent research literature and international standards (Eurocode, AASHTO, ACI, FEMA, FiB, etc.). A Case study of existing bridge assessment, subjected to aging and deteriorating processes, is presented. The effectiveness of inspection planning tests and procedures is also examined, particularly when original project technical reports and construction certificates are missing. Through experimental data, probabilistic assessments of structural reliability, and degradation modeling, the interpretation of test results is reviewed to accurately quantify the extent of damage and the implications for the remaining service structural life.