The Fern Hollow Bridge Collapse: A Wake-Up Call for Bridge Maintenance Programs

Elizabeth Ruiz

Posted 3/20/2024


The National Transportation Safety Board announced last month that the 2022 collapse of the Fern Hollow Bridge in Pittsburgh was caused by critical lapses in bridge maintenance and oversight by multiple agencies.1

A structural failure caused the bridge to fall ~100 feet, collapsing onto 6 vehicles in the park below and injuring 4 people. It is another unfortunate reminder of the importance of reliability and maintenance in infrastructure.

NTSB Chair Jennifer Homendy reminds us, “​​The Fern Hollow bridge catastrophe must serve as a wake-up call that we cannot take our infrastructure for granted. 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.”

This week’s newsletter will cover the NTSB’s description of the failure, differentiate between failures and breakdowns, and provide quick tips on bridge maintenance. 

poor bridge maintenance was the cause of this incident
Image Courtesy NTSB

Failure of Bridge Maintenance

Here is NTSB’s breakdown of the incident:

  • NTSB investigators determined that the collapse started with a failure of the transverse tie plate on the southwest bridge leg. 
  • The failure was caused by extensive corrosion and section loss.
  • The corrosion and section loss were the result of continual accumulation of water and debris, preventing the formation of a patina.
  • Repeated maintenance and repair recommendations were documented in many inspection reports, but the City of Pittsburgh did not act on them.
  • The lack of action led to the deterioration of the fracture-critical transverse tie plates and the structural failure of the bridge. 

Along with inaction by the city on inspection recommendations, NTSB investigators discovered that PennDOT contractors working on behalf of city conducted inspections that… 

  • were not compliant to guidance 
  • did not identify fracture-critical areas on the bridge’s legs
  • did not accurately calculate load ratings 

NTSB investigators determined that three main aspects of the load rating calculation were not accurate:

  • How holes and section loss on portions of the bridge legs were handled
  • The effective length factor used to estimate bridge legs’ ability to resist buckling
  • The amount of asphalt wearing surface on the bridge at the time of the collapse

If the load rating calculation had taken these factors into consideration, they would have found that the bridge needed to be closed. 

Due to this oversight at the city, state, and federal level, the NTSB has chosen to issue 11 new recommendations to the Federal Highway Administration, PennDOT, the City of Pittsburgh, and the American Association of State Highway and Transportation. 

Check out the new recommendations here. Click to see the public docket for the investigation. Read the interim NTSB report sent to the FHWA. 1

(all information courtesy NTSB)

What is the Difference Between a Failure and a Breakdown?

Now that we have gone over the different failures that led to the bridge collapsing, let’s differentiate between a failure and a breakdown.2

What is a failure? According to IDCON INC, a failure is when the equipment condition reaches an unacceptable level. This can include high temperature or vibration levels, too little flow, etc. If the equipment is left to operate, the failure will develop into a breakdown.

The breakdown is the point where the equipment stops functioning, which can lead to safety incidents, lost production, unplanned shutdowns, and incur cost.

The time between a failure converting to a breakdown is called the Failure Development Period. 

Image Courtesy IDCON INC

As you can see in the image, the Inspection phase of the Failure Developing Period is critical to stopping the breakdown from occurring. In the case of the Fern Hollow Bridge collapse, inspections were performed and reported by the city, but not acted on, and some inspections were done incorrectly by PennDOT contractors. The failures (extensive corrosion and section loss) found in the city’s inspections were reported but not repaired, and the load rating calculation by PennDOT was incorrect (leading to further wear), so the problems developed to the point that the bridge collapsed.

Bridge Maintenance Tips

A well-developed bridge maintenance program is essential for public safety and the safety of reliability engineers and maintenance techs working on them. Bridge failures are not only dangerous but can be very costly. Waagner Biro Bridge Services has put together a list of basic bridge maintenance tips to be aware of when handling bridges.3

Why is bridge maintenance essential?

  • Safety assurance
  • Economic benefits and longevity
  • Preventive care
  • Keeping the trust of the public
  • Environmental considerations

According to Waagner Biro, creating a bridge maintenance schedule that encompasses the specific needs of the structure is important for engineers and technicians to keep on track. The frequency of bridge maintenance will vary depending on the age of the bridge, the material it was built from and what environment it is exposed to, and the design. Best practice is to perform a thorough inspection once every 2 years, but conditions/heavy traffic may necessitate more frequent inspections. 

bridge maintenance

5 Key Bridge Maintenance Tips:

Regular Inspections: Thoroughly inspect all parts of the bridge, including structural components, surface, and foundation. Wear, corrosion, or signs of other damage must be included in the inspection report and addressed as soon as possible.

Timely Repairs: Immediately addressing failures found in inspections is crucial to bridge maintenance, as we see in the Fern Hollow Bridge incident. Delayed repairs can lead to deterioration and increase the risk of an unsafe breakdown. 

Cleaning and Debris Removal: Regular cleaning and debris removal is a vital task that is often overlooked in bridge maintenance. Leaves, dirt, and trash can accumulate, leading to drainage problems and corrosion. 

Corrosion Protection: Another aspect of bridge maintenance we were reminded of by Fern Hollow. Corrosion protection includes application of protective coatings, ensuring proper drainage to avoid water accumulation, and using corrosion-resistant materials when designing, constructing, and repairing bridges. 

Load Management: Load management for bridges includes monitoring the weight and type of vehicles that are permitted to use the bridge, ensuring they are within the load capacity (which much be calculated correctly). Overloading causes undue stress on the bridge which can lead to damage and reduce the lifespan.3

(information courtesy Waagner Biro)


The Fern Hollow Bridge collapse underscores the critical importance of diligent bridge maintenance and oversight. The incident, caused by extensive corrosion and section loss that went unaddressed despite repeated recommendations, serves as a stark reminder of the potential consequences of neglecting infrastructure maintenance. 

The breakdown highlights the need for accurate inspections, timely repairs, and load rating calculations to prevent such catastrophic events. Implementing a comprehensive bridge maintenance program, including cleaning, corrosion protection, and load management, is essential for ensuring public safety, worker safety, and the longevity of infrastructure.


Maintenance and Oversight Failures Led to 2022 Pittsburgh Bridge Collapse. February 21, 2024. NTSB Blog. National Transportation Safety Board. 

Failure vs. Breakdown: What is the Difference Between a Failure and a Breakdown? Tor Idhammar. IDCON INC. YouTube Video.

Essential Bridge Maintenance Tips. February 12, 2024. Waagner Biro Bridge Services. Blog post. 

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