What does poor rating for collapsed bridge mean for others? | Technology

HOW DO BRIDGE INSPECTIONS WORK?

The Federal Highway Administration's bridge inspection program was developed after the 1967 Silver Bridge collapse in West Virginia, which killed 46 people. It has expanded over the years to include state- and municipally owned bridges, not just those in the federal highway system, and to include rules for underwater inspections and regulations for qualifications of inspectors.

Generally, bridges are inspected every two years, with some older or lower-rated bridges inspected more often.

The municipal or state entities that own and maintain the bridges submit those inspection reports to state departments of transportation, which are required to provide them to the Federal Highway Administration.

WHAT DOES A POOR DESIGNATION MEAN?

Inspectors, who are trained engineers, largely perform detailed visual inspections of the three major structures of a bridge — the deck on which vehicles drive, the structure that carries the deck, and the substructure or culverts that hold up that superstructure. Other inspection methods are used underwater or when needed to determine whether corrosion has affected the weight a bridge can carry.

If any of the three structures of a bridge is rated 4 or below on a 9-point scale, the bridge is rated as poor, said Andy Herrmann, past president of the American Society of Civil Engineers.