What is the importance of the Bay Bridge in the novel, Earth Abides?

The Bay Bridge is where Ish finds an abandoned car that he remembers until his dying day. Ish wonders about that driver and whether the owner had simply jumped from the bridge after the disaster of the virus attack. Ish considers the bridges a sign of civilization and notes that those signs hang on past the time much of civilization fades away. Ish dies just off that bridge, having been carried across it one last time by his great-grandson, Jack.