London Bridge Isn't Necessarily Falling Down, Guys

A "structurally deficient" bridge can safely stay in service if weight limitations are posted and observed and the bridge is monitored, inspected, and maintained. A bridge designed in the 1930s could be deemed "functionally obsolete" because it's narrower than modern standards dictate or because its clearance over a highway isn't up to modern snuff, not because it's in danger of tumbling down.