[20150306]IN10241_缺桥数再次下降.pdf

CRS INSIGHT Prepared for Members and Committees of Congress INSIGHTINSIGHTi i Deficient Bridge Count Drops Again March 6, 2015 Recent news reports on the condition of highway bridges, based on newly released data from the Federal Highway Administration (FHWA), generally focus on the large number of bridges classified as deficient or on an increase in deficient bridges in a particular state. These reports, however, tend not to address the overall decline in the number of deficient bridges in 2014 and the long-term downward trend, particularly among bridges posing structural safety concerns. Two Types of Problem Bridges FHWAs National Bridge Inventory classifies deficient bridges in two categories: structurally deficient and functionally obsolete. FHWA considers a bridge to be structurally deficient “if significant load-carrying elements are found to be in poor or worse condition due to deterioration and/or damage, or if the adequacy of the waterway opening provided by the bridge is determined to be extremely insufficient to the point of causing intolerable traffic interruptions.” Structurally deficient bridges are the ones whose physical condition poses the greatest risks to motoris