Caltrain Downtown Rail Extension

As part of the broader Downtown Rail Extension (the Portal) project, 4th & Townsend Station replaces the existing surface level 4th & King terminal station with a new underground station. This change unlocks the possibility of extending regional rail into the Salesforce Transit Center, integrating Caltrain with California High-Speed Rail and reinforcing San Francisco’s role as a true regional hub.

At the surface, station headhouses establish new points of entry while respecting the urban fabric of the South of Market neighborhood. Beneath Townsend Street, a large cut-and-cover station box will accommodate both Caltrain and future CAHSR tracks, creating capacity for expanded service and intercity connections.

The design emphasizes clarity and efficiency, with headhouses at street level providing vertical circulation down to the platforms. The station box beneath Townsend Street is organized to support both current Caltrain operations and eventual CAHSR service, ensuring a flexible, long-term framework. This subterranean configuration not only resolves today’s surface-level congestion but also sets up the rail corridor for its next century of use.

Robin Chiang & Company produced schematic drawings for the design-build contract procurement, and is currently working on various enabling projects to set up the framework for this project’s construction.