By David Shepardson

WASHINGTON The National Transportation Safety Board on Thursday urged federal and state officials to improve maintenance oversight for more than 10,000 U.S. bridges made of a specific type of steel, based on its review of a 2022 bridge collapse in Pittsburgh.

The NTSB said officials should make sure any problems identified in inspection reports are addressed for bridges made of uncoated weathering steel. The 447-foot-long Fern Hollow Bridge in Pittsburgh fell approximately 100 feet after a structural failure, injuring four people.

More than 10,000 bridges in the United States are made of uncoated weathering steel and can be used for decades if properly used and maintained, the NTSB said.

NTSB investigators found annual inspections of the Pittsburgh bridge identified blocked drainage for the 10 years prior to the accident, but it was not corrected. NTSB investigators found other Pennsylvania bridges with similar issues with drainage, debris accumulation and corrosion.

Adequate drainage is necessary to allow the uncoated weathering steel to dry off after rain to prevent corrosion and structural weakening.

President Joe Biden said in 2022 the Pittsburgh accident underscored the urgency of rebuilding U.S. infrastructure.

The NTSB wants the Federal Highway Administration to develop a process for making sure owners of bridges made with uncoated weathering steel perform needed maintenance and fixes. The agency did not immediately comment.

(Reporting by David Shepardson; Editing by Cynthia Osterman)