State and local highway officials should work with the Federal Highway Administration to develop a bridge-design quality-control program and to revise a bridge inspection manual to include guidance on load ratings, according to NTSB officials at the annual International Bridge Conference. Their investigation of the collapse of the I-35 bridge in Minnesota in 2007 revealed that visual inspections did not detect flawed gusset plates. The agency has since designed software to aid gusset-plate inspection.

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