As the first anniversary of the 2022 Fern Hollow Bridge collapse in Pittsburgh draws near, the National Transportation Safety Board has released an update about its probe of the accident but has not yet determined the probable cause of the collapse. The NTSB says it is continuing its investigation.

In the investigative update, released on Jan. 26, the safety board also said, “All aspects of the collapse remain under investigation while the NTSB determines the probable cause, with the intent of issuing safety recommendations to prevent similar events.”  The report also notes that its information is "preliminary and subject to change."

Cautionary Note

Along with the update of its investigation, the safety board opened the public docket for its probe, including 2,137 pages of information related to the collapse. 

But the board cautioned that “no conclusions about the cause of the collapse should be drawn from the information within the docket.” 

The board said that its investigation to date has included interviews with personnel from the City of Pittsburgh, the Pennsylvania Dept. of Transportation and consulting firms that were involved in maintaining, inspecting and doing oversight of the bridge.  

The NTSB said that information from those interviews was not included in the public docket, but will be added to it “at a later date.” 

Steel Tests

The report said engineers in the NTSB’s materials laboratory have studied “multiple fractures” on the steel legs of the bridge after the collapse and did 3D scans of those areas of the legs.

The safety board said “extensive mechanical and metallurgical testing” of the bridge’s weathering steel, undertaken at the Federal Highway Administration’s Turner Fairbank Research Center “is nearing completion.” The NTSB report said results of those tests “will be compared to the material specifications referenced in the bridge’s original design plans.” 

Moreover, team members did “limited investigations” of 10 steel-frame bridges across Pennsylvania that had design elements or other features similar to Fern Hollow’s K-frame and uncoated weathering steel. 

The NTSB also said it has gathered documentation from local state and federal agencies. 

On Jan. 28, 2022, the 447-ft-long steel K-frame bridge fell about 100 ft onto the park below it. At the time of the collapse, there were six vehicles with nine occupants total on the bridge. 

In a May 5, 2022, update the NTSB said two vehicle occupants had serious injuries, two others had minor injuries, four were not injured and “the injury status of one person was unknown.” There were no fatalities.

A replacement bridge, whose cost was initially estimated at $25 million, was built and opened to traffic in late December, less than 11 months after the collapse.