Weaving its way through San Francisco, Highway 101 has carried traffic off Interstate 80 from the Bay Bridge into The City and down the peninsula for the past 70 years. Running through the Mission District to Candlestick Point, this stretch of concrete pavement infrastructure from Mile Post 0.0 to Mile Post 5.4 has finally reached the end of its service life. The work currently underway, the SF 101 Rehabilitation Project, will modernize this stretch of freeway, and is an important component of Caltrans’ “Fab 4” initiative to restore San Francisco’s major freeways.

To extend the roadway lifespan of this portion of Highway 101, Vanguard Construction, working under a Construction Manager/General Contractor (CMGC) contract with Caltrans, is rehabilitating 15.4 lane miles of concrete pavement, restoring the structural integrity through the modernization of heavily damaged center medians, rehabilitating on- and off-ramps, replacing aging Type 50 median barriers with modern Type 60M barriers, and upgrading safety devices, striping, and signage.

Type F Concrete Barrier Rail is installed in advance of the roadway reconstruction work.

The existing concrete pavement on the mainline (freeway lanes) is being replaced with high-performance Continuously Reinforced Concrete Pavement (CRCP), which will ensure a long, extended lifespan, provide a smoother surface, and significantly reduce the need for maintenance.

Demo work takes place to access the hillside drainage system for reconstruction prior to the new concrete pavement work.

For the associated I-80/US 101 Viaduct Project, which started early this year, crews are applying a polyester overlay to the San Francisco Bay Bridge decks that connect I-80 to Highway 101 to strengthen and protect the structures.

Initial work began on the SF 101 Rehabilitation Project in October 2025, and is scheduled for completion in early 2028. Approximately 10 lane miles of the 15.4 within the project will receive a full concrete pavement replacement, with the balance of the rehab work involving slab replacement.

At full-depth excavation to examine the original 70-year-old drainage system, measurements are taken in preparation for the installation of new drainage piping.

Vanguard Project Manager Jackson Lacombe provided an overview of the project. “This project is uniquely challenging because it is a major, high-visibility rehabilitation of one of the Bay Area’s most critical and constrained freeway corridors,” Lacombe stated. “The work is on U.S. Highway 101 in San Francisco, a segment that serves as a primary ingress/egress to downtown, ties directly into the 101/80 interchange, and carries very high volumes with limited or no shoulders in many areas,” he continued.

“That combination compresses staging options, limits recovery space, and makes routine construction decisions – access, work zones, lane reductions, and detours – disproportionately impactful to mobility, safety, and public perception,” Lacombe explained.

He stated that preconstruction is complete, and they are now in the early stages of construction. “We are meeting these challenges by executing the plan developed through the CMGC process – where constructability, sequencing, and schedule certainty were addressed up front before the most disruptive work began,” Lacombe continued.

Existing barrier removal takes place on the Highway 101 Hospital Curve.

“Our focus now is on implementing the planned sequencing and work methods to reduce the number of closures, compress durations, and maintain safe throughput, specifically targeting closure fatigue in the region,” he detailed, “and continuing close coordination with stakeholders and adjacent projects to avoid stacking impacts and align allowable weekends/work windows.”

Project Manager Jackson Lacombe summarized well what Vanguard is facing and how they’re addressing this unique and highly visible project. “Overall, the challenge is delivering a broad modernization effort on a tight, shoulderless, high-demand urban freeway – while keeping the region moving and maintaining public confidence. Our approach is to execute the work plan built around the corridor’s constraints, minimize disruption through smart sequencing and coordination, and keep schedule performance tightly managed as construction ramps up.”

To accomplish some of those goals involving minimizing disruption and schedule performance, four full-freeway weekend closures will take place between late 2027 and mid-2028.

Big thanks and a tip of the hard hat go out to Vanguard Project Manager Jackson Lacombe and Caltrans District 4 PIO Lori Shepherd for their contributions to this story.