Ghost Freeways

In the late 1950s the state built two double-deck concrete viaducts into San Francisco. Both had southbound traffic on top and northbound below. Both were meant to go further, and both were stopped short by the city's freeway revolt. One earthquake on 17 October 1989 closed them both. Neither came back.

The Embarcadero Freeway (I-480) carried Bay Bridge and Bayshore traffic along the waterfront, past the Ferry Building, to a dead end at Broadway. It was built in three contracts from May 1955 and finished to Broadway in early 1959. It was California's first double-deck freeway, alongside Oakland's Cypress Street Viaduct. Demolition began on 27 February 1991.

The Central Freeway (US-101) left the James Lick Freeway on a 1955 steel viaduct, became a concrete double deck near Market Street, ran up the east side of Octavia Street, and ended at Turk and Gough, a block west of Civic Center. It came down in three stages: north of Fell in 1992, the upper deck in 1996, and the rest in 2003. Octavia Boulevard opened on its land in 2005.

This page collects the project's research into one place. It is built from period engineering drawings, the state highway magazine, old topographic maps, parcel lines and lidar, and it is checked against ten period photographs. Every figure below is drawn from the project's route and structure data.

Both freeways are rebuilt from the same route and structure data as the drawings below, standing over a model of today's city: USGS terrain, today's street map and see-through OpenStreetMap buildings. Drag to move, pinch or scroll to zoom, and twist or right-drag to turn. Switch between 1959, new and pale, and 1989, weathered, as the earthquake found them. Every map and photo comparison on this page has a See in 3D button that takes the model to the same spot.

Coming off the Bay Bridge approach at Rincon Hill, the freeway crossed Folsom, ran northeast parallel to it past the old Transbay Terminal, and then curved north onto The Embarcadero between Folsom and Howard. From there it ran straight up the waterfront, across the foot of Market, past the Ferry Building and on to Broadway. At Broadway a double-deck ramp turned west toward Battery and Sansome, and a short stub pointed north toward a Golden Gate extension that was never built.

To place it today: north of Mission St, the Muni E/F streetcar tracks in The Embarcadero median run under the old deck, within about 8 m of its centerline. If you stand on the F-line platform opposite the Ferry Building, you are under where the double deck was.

Why so tall? The lower deck sat about 11 m above the street, higher than on the sister Cypress Viaduct in Oakland, because the State Belt Railroad ran beneath it. With a 7.5 m deck-to-deck spacing, the upper roadway was about 18.5 m up and its railing about 20 m (66 ft). That fits the popular "70 feet high" figure.

The Central left US-101 at the 13th St / Division interchange on the 1955 steel viaduct, which still stands. West of South Van Ness it became a single-level concrete viaduct, stacked into two decks just before Market and crossed Market on one long prestressed span. North of Market it ran over the lots on the east side of old Octavia Street. At Laguna a NB exit dropped to Fell and a SB entrance rose from Oak. Just north of Fell it swung NNE on a diagonal across Hayes, Grove, Fulton and McAllister. Near Golden Gate it split: the upper deck went down to a SB on-ramp at Turk and Gough, and the lower deck went down to a NB off-ramp at Franklin and Golden Gate.

To place it today: the double deck's 110-ft right-of-way was the strip just east of old Octavia St. That strip is now the east half of Octavia Boulevard and the "Central Freeway parcels", such as Parcel T at 188 Octavia. North of Fell, diagonal lot lines in today's parcel map still trace its path.

Which way on top? This project first assumed the Central's upper deck carried northbound traffic. The primary source says otherwise: "Southbound traffic uses the top level while northbound traffic travels on the lower level" (CHPW May–June 1959, p. 41). Later events agree. When the upper deck came off in 1996, the remaining deck carried only northbound traffic, and the SB Oak St on-ramp went with the upper deck.

Both freeways used the same structural system, described by the district construction engineer in 1957: "a continuous reinforced concrete box girder viaduct, of repeating 80-foot span, supported by reinforced concrete bents on steel piles." Each bent is a two-storey portal frame. The lower cap is reinforced concrete with fixed column joints. The upper cap is post-tensioned and pinned onto its columns. The columns are plain rectangular prisms in board-formed concrete, with no capitals or flares. From below, the soffit reads as a flat, smooth slab bounded by the cap beams.

For each of ten period photographs, camera position, heading and field of view were solved from landmarks at known bearings: the Ferry Building tower, Coit Tower, the Transamerica Pyramid and the City Hall dome. The 3D model then rendered the same view. The photos belong to their archives, so they are linked, not reproduced: open each one next to our render. Heights were checked as ratios at a bent, using the 7.5–7.6 m deck-to-deck spacing as the scale. They agree within about 1 m at four sites. The renders come from the current model, the same one as in the explorer above: See in 3D puts you at the photographer's position to look around.

No single source gives the whole picture. The alignment comes from a 1973 topographic map registered to today's streets. The structure comes from as-built drawings reproduced in a 1998 earthquake report. The words, dates and deck directions come from the state highway magazine. Parcels, lidar and photographs check all three.