Pennsylvania's Bridges

Of 22,291 total bridges in Pennsylvania, 42.9% are either structurally deficient (5,532) or functionally obsolete (4,028). (1)

Definitions -
A structurally deficient bridge is closed or restricted to light vehicles because of its deteriorated structural components. While not necessarily unsafe, these bridges must have limits for speed and weight.
A functionally obsolete bridge has older design features and, while it is not unsafe for all vehicles, it cannot safely accommodate current traffic volumes, and vehicle sizes and weights.

For a county-by-county list of such bridges in the state, see
Deficient major bridges in Pennsylvania - Bridge Collapse - MSNBC.com