- The Francis Scott Key bridge was "fracture critical," authorities said Wednesday.
- That means if one vital piece of a bridge fails, the entire structure could crumple.
- Of the 615,000 bridges in America, 17,468 are fracture critical, the NTSB said.
The deadly Baltimore bridge that collapsed Tuesday was "fracture critical," the National Transportation Safety Board (NTSB) said in a briefing Wednesday.
That means there's no redundancy built-in; if a single vital piece of the structure were to fail, either a part or the entire bridge could crumple.
NTSB chair Jennifer Homendy said, "the preferred method for building bridges today is that there is redundancy built in."
This includes additional protective structures or the ability for a bridge to share the load in the event of a failure, she said.
Fracture-critical bridges are a minority in America — but the Francis Scott Key Bridge isn't alone.
Of 615,000 bridges in the United States, 17,468 are fracture critical, Homendy said, citing data from the Federal Highway Administration.
She added that the Key Bridge was in "satisfactory condition" and last underwent a fracture critical inspection in May 2023.
The bridge was built in 1976 and was made of three spans totaling 9,090 feet in length, Homendy said. On average, 30,767 vehicles crossed it daily.
The shocking collapse on Tuesday raised questions about the safety of America's infrastructure, including whether the bridge's age meant its protections were outdated.
It's unclear if possible protections like a group of pilings called "dolphins" or buffering "fenders" would have made a difference. Some experts told BI that nothing could have withstood the Dali cargo ship's massive blow.
On Wednesday, the NTSB revealed the ship radioed for help from nearby tugboats for help minutes before it crashed. But it was too late, according to data the NTSB retrieved from the ship's Voyage Data Recorder (VDR.)
Two construction workers were rescued after the crash, while six were presumed dead. Two victims were recovered from a submerged red pickup truck, authorities said Wednesday.