A new report says that more than 50,000 bridges are structurally deficient. Source: Wikipedia

A new report finds that there is the equivalent of one “structurally deficient”-rated bridge, on average, for every 27 miles of interstate highway in the United States. The 1,800 structurally deficient interstate bridges are crossed 60 million times daily.

The analysis comes from the American Road & Transportation Builders Association, which looked at U.S. Department of Transportation data. The trade group's analysis says that 54,259 of the nation’s bridges are rated structurally deficient. If placed end-to-end, those bridges would stretch 1,216 miles, or nearly the distance between Miami and New York City.

The pace of improving the nation’s inventory of structurally deficient bridges slowed in 2017, the trade group says. At the current pace of repair or replacement, it would take 37 years to remedy all of them, says Dr. Alison Premo Black, chief economist.

To help ensure public safety, bridge decks and support structures are regularly inspected for deterioration and remedial action. They are rated on a scale of zero to nine — with nine meaning the bridge is in “excellent” condition. A bridge is classified as structurally deficient and in need of repair if the rating on a key structural element is four or below.

The report says that Iowa (5,067), Pennsylvania (4,173), Oklahoma (3,234), Missouri (3,086), Illinois (2,303), Nebraska (2,258), Kansas (2,115), Mississippi (2,008), North Carolina (1,854) and New York (1,834) have the most structurally deficient bridges.

(Read "Built in the U.S.A.: Replacing 559 Bridges in 3 Years.")

The District of Columbia (8), Nevada (31), Delaware (39), Hawaii (66) and Utah (87) have the least.

At least 15 percent of the bridges in six states — Rhode Island (23 percent), Iowa (21 percent), West Virginia (19 percent), South Dakota (19 percent), Pennsylvania (18 percent) and Nebraska (15 percent) — fall in the structurally deficient category.