Structurally Deficient: If a bridge is structurally deficient it means there are elements of the bridge that need to be repaired or monitored. A bridge labeled structurally deficient is not necessarily unsafe; it means they must be maintained, inspected and monitored.
Most deficient bridges are left open to traffic during its maintenance and repair, and if inspectors find unsafe conditions they can close the bridge or restrict it to light vehicles with lowered speed limits.
Functionally obsolete: A bridge that is functionally obsolete is not necessarily unsafe, it just means the bridge has older design features not built to today’s standards. A functionally obsolete bridge is not wide enough or tall enough, so it cannot safely accommodate current vehicle sizes, weights and traffic volumes.