There will be two types of track installed for the Central Subway: direct fixation track in the tunnel and embedded track on the surface street. Direct fixation track consists of rails held in place with special rail fasteners which are anchored into concrete placed on the bottom of the tunnels. Embedded track is attached to concrete slabs located below the pavement. Concrete pavement is then placed so that only the tops of the rails are visible.
There will be one passenger station on the surface located between Bryant and Brannan Streets. Besides construction of the surface station, the only visible trackwork construction on the surface will be on 4th Street between the tunnel portal at Bryant and the tie-in with the existing system at King Street.
The two tracks (northbound and southbound) will run in the middle of 4th Street and have both exclusive and shared tracks to accommodate vehicle traffic. Construction of trackwork will begin with the excavation of the existing street paving followed by placement of a concrete track slab. Embedded track will then be installed along with the track concrete pavement. The trackway pavement will be furnished with appropriate paving pattern and low profile speed bumps similar to the existing pattern on the T Third Line to provide a seamless interface between the existing and new trackways.
Partial street closures will be expected along with intersection closures during construction. Major construction activities will occur at the 4th and King intersection, where special trackwork will be installed to connect the existing and new rail systems. This work will be scheduled on three-day holiday weekends, with vehicle traffic maintained or detoured during that time.
For information about the Trackwork, Systems, and Surface Station contract, please visit the Contracts page.