Safety and maintenance regulations applicable to all bridges over 20-feet in length, located on publicly owned highways and roads everywhere in the United States are formulated and enforced by the Federal Highway Administration (FHWA), through its Office of Bridge Technology.
Administration of federal bridge funding
Federal funds to assist state and local governments in inspecting, repairing or replacing bridges is provided under the Highway Bridge Replacement and Rehabilitation Program (HBRRP). Allotment and distribution of HBRRP funds is based on needs as determined bridge inspection data gathered by state and local governments and reported to the federal National Bridge Inspection Program.
In 1978, Congress determined that the number of bridges classified as either "structurally deficient" or "functionally obsolete" had reached dangerous levels and acted to greatly increase federal funding for bridge inspection and safety. Congress' action resulted in the creation of many of today's bridge safety programs, like the National Bridge Inventory and the National Bridge Inspection Standards.
Bridge safety classifications
The FHWA defines structurally deficient bridges as those that "have been restricted to light vehicles, require immediate rehabilitation to remain open, or are closed." This classification should not be confused with "functionally obsolete," which are bridges whose capacities no longer support the roads they serve due to factors like inadequate lane width or load height clearance. While you will often see these two categories reported together, structurally deficient bridges are those considered the most likely to suffer structural failure. Most structurally deficient bridges are left open to traffic while they undergo maintenance and repair.
"As of 2003, 27.1% of the nation's bridges (160,570) were structurally deficient or functionally obsolete, an improvement from 28.5% in 2000. In fact, over the past 12 years, the number of bridge deficiencies has steadily declined from 34.6% in 1992 to 27.1% in 2003. The Federal Highway Administration's (FHWA's) strategic plan states that by 2008, less than 25% of the nation's bridges should be classified as deficient. If that goal were met, 1 in 4 bridges in the nation would still be deficient. There were 590,750 bridges in the United States in 2000; however, one in three urban bridges (31.2% or 43,189) was classified as structurally deficient or functionally obsolete, much higher than the national average. In contrast, 25.6% (118,381) of rural bridges were classified as structurally deficient or functionally obsolete." -- American Society of Civil Engineers Bridge Report Card 2005
How states use federal bridge funds
Under the federal Highway Bridge Replacement and Rehabilitation Program, each state is eligible to receive funds based on its share of the total cost to repair or replace all structurally deficient bridges nationwide.
Most states also allocate a portion of their own budgets to bridge maintenance, especially bridges that are not part of the federal interstate highway system, and smaller bridges in towns and rural areas.
The states do have latitude in deciding how they spend their federal bridge funds. Some states choose to spend all of their funds on bridge inspection, maintenance and replacement. Other states choose to use some of the funds on traditional highway construction projects.
According to the bipartisan Surface Transportation Policy Project, annual total federal funding distributed to the states for bridge programs increased from $2.1 billion in 1992, to $4.3 billion by 2001, while actual state expenditures of those funds on bridge projects increased from $1.8 billion to $2.9 billion over the same period.