A structurally deficient bridge means that the bridge has at least one structural issue that needs to be addressed. According to the latest data from the Federal Highway Administration, about 1,900 of those 56,000 deficient bridges are on the Interstate Highway system.
Part of the problem stems simply from the fact that these structures are just old.
In fact, about 41% os US bridges are more than 40 years old and have not had significant construction work for improvement, according to a February report by The American Road & Transportation Builders Association (ARTBA).