11870b5d_oric_Significance_Rating__HSR___Description
[HSR] 4 [Examples] Large plate girders with good historic integrity. Extremely large, old, or unusual steel stringer bridges. Concrete girders. Exceptional concrete t-beams. Small riveted truss bridges with no unusual details or early construction date. [Description] 
These bridges are noteworthy, but may still be relatively common. Bridges here are generally at high-risk, and this rating should be balanced with the idea that bridges in this area of the scale are generally common, but due to fairly old designs, are also rapidly being demolished.
HistoricBridges.org - Historic Significance Rating (HSR)
Description