Beneath the gentle hum of traffic and the occasional rumble of trucks, the Fern Hollow Bridge, located in Pittsburg, Pennsylvania, carried traffic over a deep ravine. Built in 1973, it replaced a bridge that had been built in 1901.

The structural steel in the bridge wasn't coated. Instead, the weathering steel alloy used was expected to 'grow' a patina that could protect the steel for over 100 years through repeated wet-dry cycles.

One early morning in January of 2022 a city transit bus was crossing the bridge. The bus had cameras installed facing both the front and rear right side and recorded the bridge collapse as it happened with the rear right side camera. Luckily, because of the early hour, there were only 5 vehicles on the bridge at the time of the collapse and no one was fatally injured.

Even though the bridge was inspected every two years, and then every year starting in 2014, inspection reports over the years found drains clogged with debris which allowed water and salt to run down the legs of the bridge and collect. This prevented the protective patina from forming. The bridge's ultimate failure was due to corrosion at the base of its 'legs'. The collapse was ruled a preventable accident—a reminder of the consequences of neglect.

The NTSB, in it's final report, cited contributing factors of lack of maintenance and repairs needed to keep it safe. Even though corrosion might start small, almost imperceptibly, but left unchecked, it could bring even the mightiest structures to their knees.