Bridge collapse in Pittsburgh’s Frick Park
Commenters in this thread are making a lot of generalizations about tax structures and so on, but it important to keep in mind this is a special case at a number of levels.  Pittsburgh has an unusually large number of bridges.  These bridges were built during times of relative wealth when the local steel and related industries were doing well.  Since the decline of American industry Pittsburgh has scaled way back and had to rebuild itself as a medical and technology center.  This recovery is mostly a success story, but the infrastructure cannot be maintained.  For example, the greater Pittsburgh area has some of the first suburban areas to be completely abandoned with services withdrawn, Penn Hills being a poignant example of this.  Obviously no bridges should be coming down, but there is a real problem here of how to build and maintain a modern city that is smaller than the older one that it replaces.