Transportation Infrastructure: Information on Bridge Conditions (http://www.gao.gov/products/GAO-16-72R)
GAO-16-72R: Published: Oct 29, 2015. Publicly Released: Nov 30, 2015.
QuoteBased on 2014 National Bridge Inventory (NBI) data, GAO determined that the nation has 610,749 bridges. Of those bridges, 23 percent are on the National Highway System (NHS), and this 23 percent comprise 58 percent of the nation's total deck area. The deck area of a bridge is the width of the roadway surface of a bridge multiplied by the length of the bridge, which provides an indication as to the size of the bridge. Nearly 25 percent of all bridges are deficient, with 10 percent categorized as structurally deficient and 14 percent categorized as functionally obsolete. Of bridges on the NHS, 4 percent are categorized as structurally deficient while 17 percent are categorized as functionally obsolete. State agencies own about half of all bridges and over 90 percent of NHS bridges.