University of California Transportation Center

The big news from the Bay Area's 1989 earthquake was that the transportation disruptions were only inconvenient, not dreadful. Structural failures on the Bay Bridge and several elevated concrete freeways cut major metropolitan commuting routes. Nevertheless, the regional transportation system didn't crash at the time. It was resilient because it was redundant - the parallel links took up the burden. Commuters got to work without intolerable hardship. Trucks got their freight delivered, nearly on time. Some businesses suffered in the short-term, but only a few failed. 

Estimates place direct losses from the Loma Prieta quake at over $8 billion dollars, making it the costliest natural disaster in American history at the time. In addition, some costs must be assigned to the secondary losses resulting from the breakdown in accessibility. The surprise is that the losses were so low. Our studies into the effects of breaks in the metropolitan transportation network reveal three major reasons why traffic disaster did not follow the earthquake disaster.