Caltrans details proposed Tiburon Boulevard upgrades

Plans are in the works to repair and upgrade about 4.6 miles of Tiburon Boulevard.

Caltrans presented the proposed changes at a meeting it organized on Thursday. The project, estimated to cost around $23 million, would take about a year and be completed in three segments — the western, central and eastern parts — beginning in spring of 2026.

The plan calls for upgrading or replacing guardrails, road signs, and drainage and electrical systems. It also includes upgrading curbside ramps to be compliant with the Americans with Disabilities Act, repaving roads and the addition of bike lanes.

The western segment of the project, spanning from Tower Drive in Mill Valley to Reed Ranch Road in Tiburon, includes changes to two intersections.

At East Strawberry Drive, the right turn lane onto eastbound Tiburon Boulevard would be removed and the existing bus stop on Tiburon Boulevard would be relocated. The new bus stop would be coordinated with transit authorities during the final design phase in the summer of 2025, according to Caltrans.

Class IV bikeways would be added along Tiburon Boulevard, from approximately 1,000 feet west of the freeway to Trestle Glen Boulevard. A class I bikeway at East Strawberry Drive to Greenwood Cove Drive is also planned.

The central section of the project, spanning from Reed Ranch Road to San Rafael Avenue, includes adding a class IV bike lane from Reed Ranch Road to Trestle Glen Boulevard. The Avenida Miraflores/Tiburon Boulevard intersection would be altered to remove the right turn lane from westbound Tiburon Boulevard onto northbound Avenida Miraflores.

The eastern section, from San Rafael Avenue to the Tiburon Boulevard/Main Street intersection, includes a curb extension at the Mar West Street intersection. It also would add yield lines to the Ned’s Way/Tiburon Boulevard intersection.

Tiburon Town Manager Greg Chanis said he is glad to see the proposed improvements, but hopes for better communication and coordination from Caltrans with Tiburon residents.

“We are pleased CalTrans is planning to invest significant funding into the maintenance of SR131 (Tiburon Boulevard),” Chanis said in a statement. “However, given the project has evolved from a Rehabilitation/Maintenance project to one that includes significant additional features related to bicycle/pedestrian infrastructure, we would expect CalTrans to engage in a more robust public outreach effort to residents of Tiburon and our elected officials prior to the plans being finalized.”

Andrew Poster, the Mill Valley public works director, said that while the project area is outside city limits, it would incorporate some of the biking infrastructure the city has already installed.

“The state’s project should dovetail nicely into the significant Blithedale Avenue rehabilitation project that the city recently completed, which includes class IV bike lanes, transit and pedestrian improvements,” Poster said.

Mill Valley Mayor Urban Carmel stressed the importance of continuing safe biking infrastructure throughout the county.

“They’ve been talking about this project for a long time, so I’m glad it’s moving into an implementation phase,” Carmel said. “It will all make sense when it comes together.”

Carmel said that adding safer bike lanes will help reduce traffic by making biking more appealing.

“Biking infrastructure is super important,” Carmel said. “You can’t make these roads any wider. You have to incentivize biking. Make it safer for people to ride their bike. It’s green, it’s healthy and it reduces traffic congestion.”

The public comment period is open until Friday. Comments can be emailed to SR131CapMProject@dot.ca.gov.

After the public comment period ends, Caltrans will either grant environmental approval, conduct additional environmental studies or abandon the project. The project also requires approval from agencies such as the state Department of Fish and Wildlife and the California Transportation Commission.