Every day 185 million vehicles – cars, trucks, school buses, emergency response units - cross one or more of America’s 55,710 'structurally compromised' steel and concrete road bridges, the highest concentration of which are in Iowa (nearly 5,000), Pennsylvania and Oklahoma. Nearly 2,000 of these crossings are located on interstate highways, according to the American Road and Transportation Builders Association's recent analysis of the US Department of Transportation's 2016 National Bridge Inventory.