11870b5d_oric_Significance_Rating__HSR___Description
[HSR] 3 [Examples] Average to large size pre-1940 stringer bridges. Average plate girders. Outstanding expressway overpasses with excellent historic integrity and uncommon design. Average concrete t-beams. Concrete arch bridges with below-average historic integrity. Exceptional rigid-frame bridges. [Description] 
Relatively young bridges that are nevertheless an uncommon structure type, or otherwise have enough significance to be higher than 2.
HistoricBridges.org - Historic Significance Rating (HSR)
Description