National Transportation Safety Board Chairwoman Jennifer Homendy presides over the online NTSB meeting discussing the cause of the 2022 collapse of the Fern Hollow Bridge on Wednesday, Feb. 21, 2024.

The Fern Hollow Bridge in Pittsburgh’s Squirrel Hill neighborhood collapsed two years ago as a result of “multiple failures” by bridge inspectors and city, state and federal officials to properly care for the bridge, the National Transportation Safety Board ruled Wednesday.

But board chairwoman Jennifer Homendy laid the major responsibility on the city as owner of the bridge, which had been rated in poor condition for more than 10 years. The city failed to act on up to 27 years of routine bridge maintenance recommendations, with inspectors warning about deteriorating conditions every one or two years.

“It really was a cascade of failures,” Homendy said when asked about the cause in an online interview with Pittsburgh-area reporters after the hearing Wednesday. “But specifically and ultimately the city of Pittsburgh had responsibility for the bridge.”

Since there were problems with how the city maintained the bridge, how inspectors did their work, how the Pennsylvania Department of Transportation oversaw the inspections, and even problems with the federal government’s oversight of the state, “This should serve as a wake-up call to everyone,” she said.

“It was failure after failure after failure,” she said. “There were many times where an individual or an entity or the city could have done something. That was not done. It was business as usual, year after year.”

The technical reason the bridge collapsed at 6:37 a.m. on Jan. 28, 2022, from Forbes Avenue into Frick Park was that the shoe tension tie plate at the bottom of the bridge’s southwest leg buckled because of severe deterioration, pulling the rest of the bridge down with it, the three members of the board ruled unanimously on Wednesday.

In addition to the probable cause, the board unanimously approved 19 findings of fact and made 11 recommendations for local, state and federal agencies and organizations to change procedures to avoid similar incidents in the future.

“We hope, if the board adopts them, we can prevent this sort of thing from occurring in the future despite all localities facing such concerns,” Dennis Collins, the NTSB’s lead investigator, told the board in advocating for the recommended new procedures.

Nine people were injured when six vehicles, including a Pittsburgh Regional Transit bus, dropped into the ravine. Many of the victims have filed lawsuits against the city and others.

The last finding of fact was highly critical of the city, in particular, for not performing regular maintenance recommended by inspectors but also for those inspectors not doing their job correctly.

“The Fern Hollow Bridge collapse demonstrates the consequences of failure to complete inspections in accordance with standards, failure to correctly identify fracture-critical members, failure to correctly perform a load-rating analysis, and failure of the bridge owner to respond to inspection findings and complete maintenance recommendations in a timely manner.”

City’s reasons not clear

Although the two-year investigation found a multitude of failures by everyone and every entity involved in the bridge’s inspection and maintenance, the NTSB remained perplexed by one main question: Why did the city fail to do the recommended maintenance on the bridge for decades?

Collins said in response to a reporter’s question that Pittsburgh’s “poor quality of records and the high staff turnover prevented us from getting an answer to that question.”

In a separate interview with Pittsburgh Union Progress after the meeting, Maria Montano, Pittsburgh Mayor Ed Gainey’s chief spokeswoman, said since Gainey took office only about three weeks before Fern Hollow collapsed in 2022, “We can’t say what previous administrations did or didn’t do.”

“But based on our examination, from 2005 to 2021 [the time period of inspections that NTSB relied on to do its investigation] apparently the city did not have proper personnel or resources in place” to either do the maintenance or monitor how the work was or wasn’t done.

“We do not dispute the findings of the NTSB report,” she said, including that the city has had poor record keeping and personnel problems that made it difficult to determine why Fern Hollow maintenance was not done for decades.

But because of Fern Hollow’s collapse, “the city has been much more responsible on these issues, including making sure higher priority tasks can be resolved, making sure fracture-critical sections of bridges are addressed, and has created a bridge asset management program that now charts how the city is maintaining its bridges,” she said.

“The ultimate goal,” she said, “is moving from a reactionary process to a proactive process to protect bridges for generations to come.” 

Pittsburgh uses inspectors hired by the state Department of Transportation to review the condition of bridges. PennDOT then reviews the reports, can ask questions or request changes, and forwards them to the Federal Highway Administration.

PennDOT spokeswoman Alexis Campbell said in a statement that the department has been working closely with NTSB and already has made some procedural changes. Those include a cover sheet on inspection reports highlighting major findings and automatically reviewing load limits every 10 years to make sure they are correct.

“PennDOT looks forward to continued partnership with the city of Pittsburgh and the NTSB as we work to respond to the recommendations in the report — many of which we have already proactively implemented,” the statement said.

Bridge should have been closed in 2014

The analysis by a team of NTSB investigators concluded that the bridge should have been closed in 2014 due to severe deterioration of the four steel frame legs that held it up. 

But because inspectors did not consider the critical importance of the legs — they were not identified by inspectors as fracture-critical members even though they were labeled as fracture critical on its original designs, which inspectors should have reviewed — the bridge was allowed to stay open.

Part of the definition for “fracture critical” means that if one of the legs failed, it could cause the entire bridge to collapse.

But what inspectors got wrong in their analysis — in addition to not reviewing the original designs — was inspector after inspector believed that the frame legs were only “in compression,” meaning they absorbed forces from above, and not “in tension,” meaning they also stretch, or bend, to absorb those forces. 

Homendy said inspectors did a load assessment of the bridge in 2014 and posted a 26-ton weight limit using faulty math and assumptions.

The bridge “would have, should have been closed,” she said, if inspectors would have properly considered the significant “section loss” that the corrosion on the bridge’s legs was causing to the steel.

But inspectors also did not know — and apparently did not investigate thoroughly enough — that the asphalt street surface was twice as thick — 6 inches versus 3 inches as planned by the designer in 1973.

Those two factors, if known, would have reduced the bridge’s capacity to just 3 tons, triggering its closure till the bridge was completely rehabilitated.

Despite the problems noted in the investigation with the inspectors’ work and the state’s oversight of that work, again and again the three board members on Wednesday came back to the fact that it was ultimately the city’s responsibility.

As board member Michael Graham put it: “This bridge didn’t collapse by an act of God. It collapsed from a lack of maintenance.”

The National Transportation Safety Board’s overview animation of the Fern Hollow Bridge collapse. Pittsburgh Regional Transit bus video of the collapse begins at about the 3:30 minute mark. (National Transportation Safety Board)

The board acknowledged the city has taken steps to improve maintenance, including an inventory of maintenance needs for the 146 bridges it owns, and the state has changed inspection procedures to make sure problems identified by inspectors get the attention they deserve. A report by consultant WSP showed city bridges will need nearly $500 million in improvements over the next 32 years.

But the board stressed that the city and state must follow through with those changes and charged the Federal Highway Administration with doing better oversight to make sure the changes are followed.

The two-year investigation included reviewing more than 1,900 pages of inspection reports beginning in 2005, building a 3D model of the bridge, measuring and chemically analyzing metal portions of the structure, and extensive interviews with city, state and federal officials as well as contractors and inspectors who had worked on the bridge.

Among the information they found was that holes in parts of the legs grew from 2 by 2 inches in 2005 to 12 by 12 inches over the years, but no action was taken by the city.

Roberto Leon, a construction engineering professor at Virginia Tech University who watched Wednesday’s online NTSB hearing, said he was taken by the fact that NTSB board members “seemed incredulous that all these things were missed,” from the inspectors to the city and the state.

The changes that the state and federal government have made after Fern Hollow’s collapse is telling, he said.

“The speed with which PennDOT and the FHWA fixed those issues, or attempted to fix those issues, is a testament to how scared they were” by what NTSB would find, he said.

Kent Harries, a professor of civil and environmental engineering at the University of Pittsburgh, said the report was “extremely thorough,” but he wished the board had stressed a broader view on better procedures for all bridge inspections and maintenance. 

“This is not unique to this bridge,” he said. “I’m a little bit disappointed we’re not looking more at the bigger picture.”

The recommendations include five for FHWA, two each for PennDOT and the city, and two for the American Association of State Highway and Transportation Officials to make changes in “Manual for Bridge Evaluation.”

The board called on the city to keep better maintenance records. It didn’t have records to show when the thickness of pavement on Fern Hollow was increased from 3 inches to 6 inches, which could have changed the load rating for vehicles. It also should work with PennDOT to make sure the changes it has made to increase maintenance staff are effective and that it is completing work recommended in inspections.

PennDOT should publish a report on the effectiveness of the city’s improvements and develop a yearly report on all bridge inspections across the state and how the inspection recommendations are followed.

NTSB investigators said other bridges across the country that are constructed — as Fern Hollow was, with uncoated weathering steel, which forms its own rust protection system — are safe if they are properly maintained. The bridges should be allowed to go through wet and dry cycles, but Fern Hollow deteriorated because clogged drains and other problems prevented it from being dry.

In her closing, Homendy, reading from prepared remarks, cited the paradox that officials ignored problems cited in inspections for decades but built a new bridge to replace Fern Hollow in less than a year.

She referred to a line in famed author Kurt Vonnegut’s 1990 novel, “Hocus Pocus,” that read: “Another flaw in the human character is that everybody wants to build and nobody wants to do maintenance.”

She added, “I hope our investigation changes some minds about that.”

PREVIOUSLY: Nobody looks good’: Many entities failed before the Fern Hollow Bridge did.

PREVIOUSLY: State, local and federal officials have changed bridge care since Fern Hollow collapse.

RELATED STORY: Pittsburgh moving ahead on nearly $500 million of bridge work recommended by consultant.

Ed covers transportation at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at

Sean D. Hamill