When SamTrans, the San Francisco Peninsula’s primary public transit agency, relocated its corporate headquarters to Millbrae, California, it sought to maintain its long-standing partnership with Caltrain and the San Mateo County Sheriff’s Office, which had previously shared a facility in San Bruno. Form4 partnered with the building owner to deliver a build-to-suit tenant improvement that accommodated the unique operational needs of all three agencies while supporting their continued collaboration.

The resulting 157,000-square-foot headquarters blends transit-inspired design with references to the natural ecology of the San Francisco Bay Peninsula. The project modernized the existing workplace environments for SamTrans, Caltrain, and the Sheriff’s Office, creating a flexible, contemporary headquarters that not only met but exceeded the functional requirements of each organization.

An extensive programming and space-planning process engaged more than a dozen departmental stakeholder groups across the participating agencies. Through a comprehensive change management effort, the design team guided users toward a new vision of the modern workplace. The result is an open, light-filled environment featuring collaborative workspaces, shared amenities, and flexible meeting areas. Each floor is organized around a series of activity nodes that define arrival points and major program elements, while quieter office neighborhoods are positioned between these hubs to support focused work.

The mixed-use base building includes ground-floor retail with two levels of structured parking above. Caltrain occupies the fourth floor, while SamTrans and the San Mateo County Sheriff’s Office are located on the fifth and sixth floors. Each agency is welcomed by a distinct arrival lobby that reflects its identity while maintaining a cohesive architectural language inspired by movement, transportation, and the region’s transit heritage.