WASHINGTON (Feb. 21, 2024) – Critical lapses in bridge maintenance and oversight by multiple agencies led to the collapse of the 447-foot-long Fern Hollow Bridge in Pittsburgh, Pennsylvania, the National Transportation Safety Board said at a board meeting Wednesday.
On Jan. 28, 2022, the bridge experienced a structural failure and fell approximately 100 feet into the park below. Six vehicles were on or near the bridge when it collapsed and four people sustained injuries. NTSB investigators determined the collapse began when the transverse tie plate on the southwest bridge leg failed due to extensive corrosion and section loss caused by the continual accumulation of water and debris, which prevented a protective rust layer, called a patina, from forming. Although repeated maintenance and repair recommendations were documented in many inspection reports, the City of Pittsburgh failed to act on them, leading to the deterioration of the fracture-critical transverse tie plate and the structural failure of the bridge.
“The Fern Hollow bridge catastrophe must serve as a wake-up call that we cannot take our infrastructure for granted,” said NTSB Chair Jennifer Homendy. “Only through diligent attention to inspection, maintenance, and repair can we ensure the roads, bridges, and tunnels we all traverse every day are safe for the traveling public. Lives depend on it.”
NTSB Animation – Overview of the collapse of the Fern Hollow Bridge
In addition to the repeated instances of inaction by the City of Pittsburgh on inspection recommendations uncovered by the NTSB, investigators also determined Pennsylvania Department of Transportation (PennDOT) contractors working on behalf of the city conducted inspections that were not in compliance with guidance, failed to identify fracture-critical areas on the bridge’s legs, and did not calculate load ratings accurately.
Investigators found three main aspects of the load rating calculation that were inaccurate: how holes and section loss on portions of the bridge legs were handled, the effective length factor used to estimate the bridge legs' ability to resist buckling, and the amount of asphalt wearing surface on the bridge at the time of the collapse. Had the load rating calculation correctly accounted for these factors, the result would have required closure of the bridge. Overall, the NTSB found insufficient oversight at the city, state, and federal level.
As a result of these findings, the NTSB is issuing 11 new recommendations to the Federal Highway Administration (FHWA), PennDOT, the City of Pittsburgh, and the American Association of State Highway and Transportation Officials to address the safety issues identified in the investigation to ensure other bridges in Pittsburgh and nationwide are properly inspected and maintained.
An additional recommendation to the FHWA was issued in an interim NTSB report. The NTSB urged the FHWA to develop a process for bridge owners to identify, prioritize, and perform any needed follow-up actions on bridges with uncoated weathering steel components. The NTSB classified that interim recommendation “Closed–Acceptable Action” because of the FHWA’s prompt action to address the recommendation.
The new recommendations, as well as the executive summary, probable cause, and findings of the investigation, are available on the investigation web page. The final report will be published on the NTSB’s website in several weeks.
The public docket for the investigation includes factual information such as reports, interview transcripts and other investigative materials.
To report an incident/accident or if you are a public safety agency, please call 1-844-373-9922 or 202-314-6290 to speak to a Watch Officer at the NTSB Response Operations Center (ROC) in Washington, DC (24/7).
