Fern Hollow Bridge collapsed 30m into a park injuring four people, because of poor maintenance, according to The National Transportation Safety Board (NTSB), which announced its findings last Wednesday.

The bridge collapse in January 2022 injured four people, including the driver of a bus. Credit: NTSB

Investigators found that the transverse tie plate on the southwest bridge leg failed because of corrosion and section loss. The corrosion occurred because accumulation of water and debris prevented the formation of a patina. Inspection reports documented maintenance and repair recommendations, but the City of Pittsburgh did not act on them. So the tie plate deteriorated.

Fractures on the collapsed Fern Hollow Bridge. Credit: NTSB

The NTSB also found that contractors working for Pennsylvania Department of Transportation (PennDot) carried out inspections that did not comply with guidance. These inspections did not identify fracture-critical areas on the bridge’s legs; and they did not accurately calculate load ratings. A correct calculation would have required the city to close the bridge.

NTSB has issued eleven recommendations to various agencies to ensure that bridges nationwide are properly inspected and maintained (link opens in new tab).