At 1:30 a.m., e.d.t., on June 28, 1983, a 100-foot-long suspended span between piers 20 and 21 of the eastbound traffic lanes of the Interstate Route 95 highway bridge over the Mianus River in Greenwich, Connecticut, collapsed and fell 70 feet into the river below. Two tractor-semitrailers and two automobiles plunged Into the void in the bridge and were destroyed by impact from the fall, Three vehicle occupants died, and three received serious injuries.

​We determined that the probable cause of the collapse of the Mianus River bridge span was the undetected lateral displacement of the hangers of the pin and hanger suspension assembly in the southeast corner of the span by corrosion-induced forces due to deficiencies in the State of Connecticut's bridge safety inspection and bridge maintenance program.

​We made recommendations to

• the Connecticut Department of Transportation,
  
• the Federal Highway Administration,
• the American Associatin of the State Highway and Transportation Officials,
• the U.S. Department of Transportation,
• the American Institute of Steel Construction,
• the National Committee on Uniform Traffic Laws and Ordinances.​