Congress acted rapidly and by 1968 passed the Federal-Aid Highway Act, which established the standards for bridge inspection and required states to log written inspection reports. By 1971, the National Bridge Inspection Standards (NBIS) was established and is still firmly in place.
Per the NBIS, any structure longer than 20 feet that is part of the federal highway system must be inspected every two years. Over the last 50 years, the program has continued to evolve and was expanded in 1979 to include all structures on public roads.
The collapse of Connecticut’s Mianus River Bridge in 1983 and the I-35 bridge over the Mississippi River in 2007 caused a nationwide push for heightened inspection criteria and the development of a load ratings process for specific components of truss bridges. Sadly, funding for maintenance, repairs or replacement is often at the core of these disasters.