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Before There Was BART, a Transbay Train Crossed the Bay Bridge

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Welcome to Curbed's ongoing series titled Hidden History, where Curbed highlights a Bay Area location with a secret past. Maybe it's no longer there, maybe it's been converted into something else, but each spot holds a place in Bay Area history - even if not many people know it. Have a suggestion or know a place with a secret history? The tipline's always open or you can leave a comment after the jump.

Passengers on board the first electric train to cross the San Francisco-Oakland Bay Bridge, 1939 [Photo: SAN FRANCISCO HISTORY CENTER, SAN FRANCISCO PUBLIC LIBRARY]

When the Bay Bridge opened in 1936, traffic patterns looked a little different. Early on, the bridge carried three lanes of car traffic in each direction on the upper deck, while the lower deck was for truck traffic and the inter-urban railway, including the Key System that ran through the East Bay.

Lower deck train tracks and truck traffic, 1957 [Photo: CalTrans]

Two railroad tracks on the south half of the lower deck carried the electric commuter trains of the Southern Pacific, the Key System, and the Sacramento Northern railroad. The bridge railway began service in January 1939 with routes across the bridge terminating at the San Francisco Transbay Terminal. The Key System, named because the route maps made a shape like a key, connected the city to towns like Oakland, Berkeley, and San Leandro, essentially making it possible for the East Bay to become a bedroom community for San Francisco.

Bay Bridge, with train visible on lower deck, 1946 [Photo: SAN FRANCISCO HISTORY CENTER, SAN FRANCISCO PUBLIC LIBRARY]

Cars became more popular and auto traffic increased, so in 1958, $49 million was allocated to re-configure the bridge. BY 1962, the railway system was removed and the bridge was re-aligned to carry five lanes of traffic on each deck, as it is today. The tracks that once entered the Transbay Terminal through an elevated loop were paved for buses.

Supposedly, the south wall of the Yerba Buena Tunnel on the lower eastbound deck still contains the as-built "deadman holes", regularly spaced nooks into which railway workers could duck whenever a train came along.

· San Francisco/Oakland Bay Bridge [CalTrans]
· 50 years since trains crossed Bay Bridge [SF Gate]
· Transbay Terminal: Not Always Useless, Ugly, Old & Smelly [Curbed SF]