The San Francisco-Oakland Bay Bridge spans San Francisco Bay in California. As part of Interstate 80 and the direct road between San Francisco and Oakland, it carries about 270,000 vehicles a day on its two decks, and has one of the longest spans in the United States.

The San Francisco–Oakland Bay Bridge spans San Francisco Bay in California. As part of Interstate 80 and the direct road between San Francisco and Oakland, it carries about 270,000 vehicles a day on its two decks, and has one of the longest spans in the United States. The bridge is in two sections--the western section, known as the Willie L. Brown Jr. Bridge connecting downtown San Francisco to Yerba Buena Island and the newer unnamed eastern section connecting the island to Oakland. The Willie Brown Bridge is a double suspension bridge with two decks, westbound traffic being carried on the upper deck with eastbound carried on the lower one. During the 1989 Loma Prieta earthquake, a section of the eastern span's upper deck collapsed onto the lower deck, and the bridge was closed for a month. Following the earthquake, the western suspension span underwent extensive seismic retrofitting to replace much of the structural steel supporting the bridge deck. For various reasons, the eastern span would have been too expensive to retrofit compared to replacing it, so the decision was made to replace it. Reconstruction of the eastern section of the bridge began in 2002 and was completed in September 2013. Unlike the west span and the original east span, the new east span is a single deck with the eastbound and westbound lanes on each side, making it the world's widest bridge. Demolition of the old east span is expected to last until 2018.