In what scenario might a bridge be categorized as "structurally deficient"?

A bridge is categorized as "structurally deficient" primarily when it has significant deterioration that impacts its safety or serviceability. This classification indicates that one or more major components of the bridge, such as the deck, superstructure, or substructure, have reached a condition where they may no longer perform adequately. This could involve issues such as significant cracks, corrosion, or other forms of degradation that compromise the structural integrity of the bridge. The designation serves as a critical warning for inspectors and engineers, highlighting the need for repairs or rehabilitation to ensure the continued safety of the bridge for users.

While factors like a lack of recent maintenance or infrequent vehicle use might raise concerns or indicate other issues, they do not directly lead to the classification of a bridge as structurally deficient as they do not necessarily imply immediate risk to safety or structural performance. Similarly, criteria like minimum height requirements are more related to regulatory standards rather than the structural integrity of the bridge itself. Therefore, the identification of significant deterioration directly correlates with the definition of a "structurally deficient" bridge, making it the most accurate choice in this scenario.