MILWAUKEE -- The head of the Federal Highway Administration is encouraging state transportation officials to assure the public that their bridges and roads are safe even though the investigation into the Minneapolis bridge collapse is ongoing.

Bridge safety has become a national concern after the Interstate 35W bridge collapsed in August, killing 13 people and injuring about 100.

Federal Highway administrator Rick Capka spoke at the annual conference of the American Association of State Highway and Transportation Officials in Milwaukee on Monday.

Capka said public trust and confidence is at the center of everything they do.

The Minneapolis bridge had been classified as "structurally deficient," as have more than 73,000 others nationwide.

Capka said the investigation into the cause of the Minneapolis bridge collapse will take six months to a year.