Bay Bridge

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Conceived in the Gold Rush Days, a bridge spanning the San Francisco Bay linking the cities of San Francisco and Oakland always seemed like an engineering and financial impossibility. The water separating the cities was too deep and wide. In fact, in 1921 a transbay underwater tube crossing was recommended as the best way of crossing the bay. However this idea was soon deemed inappropriate for automobile traffic.

Practical and economic concerns would make the bridge a reality. Oakland streetcar lines were laid out to feed passengers to a fleet of ferry boats traversing the bay. In 1928, ferries carried over 46 million passengers between the two shorelines. Finally, with the popularity and mass production of the automobile, it was determined that a bridge was necessary and such a structure could support itself with tolls.

Construction took three years, and was completed six months ahead of schedule. The bridge had consumed over six percent of the total steel output of the nation in 1933. Total costs were $77 million, including the construction of the Transbay Transit Terminal.

Almost as soon as the bridge was opened in 1936, traffic on the Bay Bridge exceeded levels predicted for 1950. This was partly due to the lack of other bridges crossing the bay, but also because passengers abandoned the ferry services and chose to cross via the bridge. The bridge operators lowered tolls in an attempt to lure ferry users. The strategy was successful.

In the early years, the bridge carried three lanes of auto traffic in each direction on the upper deck. The lower deck was reserved for truck traffic and the inter-urban railway, including the Key System street cars that ran through the East Bay.

Auto traffic increased greatly. In 1958, $49 million was allocated to re-configure the bridge. The railway system was removed and the upper deck was re-aligned to carry five lanes of westbound truck and auto traffic. The lower deck carried five lanes of eastbound traffic. The road deck through Yerba Buena Island had to be lowered to accommodate the large trucks that would now be allowed on the upper lanes. This work was done while traffic continued to use the bridge.

A section of the bridge was damaged in the 1989 Loma Prieta earthquake which measured 7.1 on the Richter scale. Bolts holding a section of the upper deck on the truss section sheared causing a portion of the deck to unhinge and fall onto the lower deck. The earthquake demonstrated that despite the Bay Bridge's behemoth stature and deep piers, it was vulnerable to damage during strong quakes. Retrofit work to prevent any future failures has begun.