5 states with most structurally deficient bridges Federal Highway Administration rundown spans bridges from South Dakota to Rhode Island Centennial Bridge between Davenport, Iowa and Rock Island, Illinois. (Photo: Flickr/eric wittman) The 600,000 bridges in the U.S., and the roads they connect, are crucial to the nation’s transportation network. They carry about 3 trillion vehicle miles of travel annually, accounting for about 85% of the total value of freight shipped in the U.S. However, more than 46,000 bridges are structurally deficient, according to the Federal Highway Administr...