Reinforced concrete structures face degradation due to intrinsic factors and environmental conditions. Many studies focus on using experimental testing and mathematical models to forecast the impact of corrosion and degradation phenomena on the residual safety of the structure. However, a universally accepted procedure in this respect is still lacking. This fact complicates the assessment of the safety and residual performance of degraded structures, as well as the planning of maintenance strategies. The objective of the current work is to discuss the case of the bowstring bridge over the Cassibile River in Sicily (Italy,1930s) in order to propose a philologic methodology. In fact, the absence of original blueprints makes challenging to fully understand the bridge’s construction details and the actual original safety factor of the bridge, so an exegetical approach is followed. The safety assessment of the bridge takes into account the evolution of the Italian technical codes over time, both in terms of prescribed loading and design rules. Finally, both the undamaged and degraded scenarios are taken into account for the safety assessment of the bridge using the current standard code. The results show that the bridge does not meet safety requirements due to both the increasing in loading conditions and degradation phenomena. Overall, the study highlights the importance of regular maintenance and monitoring to prevent potential safety hazards as well as the need to take into account the expected degradation phenomena beyond the simple visual findings from surveys.