Drivers on Tiburon Boulevard could hit intermittent one-way traffic control starting as early as Monday, Aug. 31, as Caltrans prepares to launch the first active construction phase of its SR-131 rehabilitation project.

The work may bring lane restrictions between 7 a.m. and 5 p.m. weekdays, according to a Caltrans traffic advisory issued Monday, Aug. 24. Crews will begin with curb ramp and sidewalk work at various intersections along the boulevard, and flaggers will be present to help motorists navigate traffic.

The Town of Tiburon confirmed the timeline in its own alert.

What's being built

The Capital Preventive Maintenance Project stretches from roughly 1,000 feet west of the US-101 interchange to the Tiburon Boulevard/Main Street intersection downtown. Caltrans reached 100 percent design in early 2026, according to the agency's project page.

Phase 1 bikeway work runs from Tower Drive, near the US-101 interchange, to Blackfield Drive. That phase introduces a temporary two-way Class 1 bike path on the inbound side of SR-131 between Strawberry Drive and Blackfield Drive.

The broader project is divided into three segments. The western segment includes Class I, II and IV bikeways, curb ramps, pedestrian refuge islands and sidewalk modifications. The central segment includes Class II and IV bikeways and intersection modifications. The eastern segment includes intersection modifications.

Timeline and what's next

Paving is not scheduled until spring 2027. Caltrans expects the full project to wrap up by winter 2027.

A July 13 Town of Tiburon advisory had noted that most high-traffic-impact work would be performed overnight. The Aug. 24 advisory makes clear that the initial curb ramp and sidewalk phase will affect daytime commuters on weekdays.

Caltrans has not yet specified which intersections will be restricted first; the agency says future traffic advisories will provide those details. Questions can be directed to Caltrans Public Information Officer Matt O'Donnell, the project contact for Marin County, at [email protected] or (510) 852-5113.

Drivers can check real-time conditions on the Caltrans QuickMap site, the 511.org travel-information service or by calling 1-800-427-ROAD.