Four major rehabilitation projects are renewing some of The City’s most heavily traveled transportation infrastructure, with concrete playing a leading role.
San Francisco can’t close for repairs. But its highways, streets, bridges, drainage systems, and pedestrian infrastructure still need those repairs. And some have needed them for quite a while.
That’s the dilemma behind an unusually concentrated collection of Caltrans District 4 projects now unfolding across San Francisco. Dubbed the Fab 4 Rehab Project Series, the effort brings together four very different rehabilitation projects designed to renew aging infrastructure while keeping one of America’s densest cities moving.
The Fab 4 includes rehabilitation of 19th Avenue/State Route 1; pavement and infrastructure replacement along U.S. 101 through Hospital Curve; rehabilitation of the 71-year-old Central U.S. 101 and Bayshore I-80 viaducts; and replacement of the aging pedestrian overcrossing above I-280 near Cayuga Park, together with additional I-280 rehabilitation.
Caltrans is coordinating the projects to reduce their collective impact on the public. Together, they are a concentrated exercise in giving existing infrastructure another generation of useful life without bringing San Francisco to a halt.
Hospital Curve construction combines demolition, slab work, and live-traffic staging in a tightly constrained urban freeway corridor.
No. 1: Rebuilding Hospital Curve
Running between Candlestick Point and the Mission District, this heavily traveled corridor of Highway 101 is receiving a complete replacement of its existing concrete pavement with continuously reinforced concrete pavement (CRCP). The project also includes drainage rehabilitation and capacity upgrades, new concrete median barriers, Transportation Management System improvements, and other safety work.
The FBD Vanguard Construction crew works to build a new median barrier on Highway 101.
Caltrans identified approximately 15.4 lane-miles of pavement for rehabilitation on this U.S. 101 corridor that carries more than 240,000 vehicles on an average day. The route serves both commuters and regional freight, making maintenance of traffic one of the central construction challenges. Caltrans and contractor FBD Vanguard Construction are using staged construction, overnight work, and precisely planned weekend closures to accomplish the job.
The choreography was on display August 21st to 24th, when two northbound and two southbound lanes between Cesar Chavez and 17th Street were closed for crucial drainage installation while two lanes remained open in each direction. Caltrans reopened all lanes at 1:03 am on Monday, August 24th, reporting that the work was completed ahead of schedule.
The Hospital Curve project is divided into three construction segments along U.S. 101 between Candlestick Point and the Mission District. Graphic: Caltrans.
The new drainage is intended to reduce flooding in wet weather and prepares the corridor for the next major operation: full northbound closures, between Cesar Chavez and 17th Street, on September 4th to the 7th and September 18th to the 21st, when crews are scheduled to continue the work and place CRCP.
Crews completed installation of the new drainage system in the median of Highway 101 on August 22nd.
Supporting that effort is another unusual piece of concrete infrastructure, one motorists may never see. Vanguard received approval to establish a temporary concrete batch plant at Pier 94 on San Francisco’s Southern Waterfront, adjacent to the CEMEX San Francisco Pier 92 Ready-Mix Concrete Plant, and just a very short drive to the U.S. 101 project site. With transport times minimized, the quality of the mix is ensured.
No. 2: 19th Avenue Crosses the Finish Line
While Hospital Curve heads into major concrete paving over two weekend closures, one member of the Fab 4 has already finished its rehab tour.
Slab replacement work takes place last December as a part of the 19th Avenue Rehab Project.
The 19th Avenue/SR-1 Project rehabilitated 18.8 lane-miles between Lincoln Way at Golden Gate Park and Holloway Avenue near San Francisco State University, including work at the Park Presidio Boulevard/California Street intersection.
Unlike Hospital Curve, this was primarily a surface-street rehabilitation project threaded through neighborhoods, businesses, shopping destinations, Golden Gate Park, and SFSU. That required a different method of keeping traffic moving while rebuilding this heavily traveled roadway, often reducing travel to one lane in each direction.
Construction began in December 2025. On August 6th, Caltrans completed the remaining paving at California Street and Park Presidio, and reopened the intersection, marking completion of the entire 19th Avenue Rehabilitation Project.
The 19th Avenue/SR-1 Rehabilitation Project extended from Lincoln Way at Golden Gate Park to Holloway Avenue near San Francisco State University. Graphic: Caltrans.
No. 3: Giving 71-Year-Old Viaducts New Life
Near the San Francisco-Oakland Bay Bridge, Caltrans is rehabilitating the 71-year-old Central U.S. 101 and Bayshore I-80 viaducts rather than replacing them. The two-year project includes repairs to bridge decks, joints, barrier rails, polyester concrete overlays, and other structural work.
Finishing work takes place in the resurfacing of the viaduct on eastbound Interstate 80 in San Francisco.
The viaducts sit within one of San Francisco’s busiest transportation hubs near the Bay Bridge. Overnight lane reductions and intermittent full closures are allowing crews to work in the constrained urban environment while extending the service life of structures motorists already depend upon every day.
Crews work on the Central/Bayshore Viaduct Rehabilitation Project with downtown San Francisco alongside the jobsite.
No. 4: A Better Way Across I-280
The fourth member of the Fab 4 brings the story down from freeway speeds to walking pace. The existing pedestrian overcrossing near Farallones Street was built following construction of I-280 in the early 1960s, connecting the Oceanview and Excelsior neighborhoods and providing access to Cayuga Park.
But its design belongs to another era.
The existing structure has an approximately 14% grade, making it difficult for many pedestrians to use. Its replacement will be ADA compliant, with grades no greater than 8%, and will widen the crossing from eight feet to 10. Improved lighting, landscaping, and artwork are also planned.
The existing Farallones Street pedestrian overcrossing above I-280.
The project reaches well beyond the pedestrian bridge.
Along I-280, the scope of work includes pavement rehabilitation, repaving ramps, upgrading concrete median barriers, rehabilitating drainage systems, and making ADA curb-ramp improvements. Bridge deck repairs between U.S. 101 and the Mariposa ramps will be topped with a one-inch polyester concrete overlay. That specific work is expected to require twelve 55-hour weekend lane reductions. Replacing the pedestrian crossing itself will require overnight full closures of I-280 in one direction at a time.
Rendering of the planned ADA-compliant replacement of the Farallones Street pedestrian overcrossing.
Rehab Without Gridlock
The Fab 4 projects don’t share identical scopes, construction methods or even modes of transportation. One replaces freeway pavement with CRCP. Another renewed nearly 19 lane-miles of one of San Francisco’s most important surface streets. A third is extending the useful life of freeway viaducts built more than seven decades ago. And the fourth combines freeway rehabilitation with replacement of a pedestrian connection between neighborhoods.
What they share is a deceptively difficult assignment: Rebuild infrastructure that San Francisco cannot afford to do without, while San Francisco continues using it. That requires staging, closures, detours, public communication, and some patience from the people caught on the other side of the orange cones. At Hospital Curve, it also requires a lot of concrete.
Rehab work takes place on the lower deck of the Bay Bridge approaching Yerba Buena Island. Photo by Caltrans.
The coming weekend closures will provide a clear demonstration of the entire Fab 4 philosophy. For a few precisely scheduled days, one of San Francisco’s most heavily traveled freeways will shut down in order to allow Caltrans and Vanguard to work around the clock to replace the pavement that has almost a quarter of a million vehicles traveling over it every single day, with new CRCP that will smoothly bear the weight of all that traffic for many more decades to come.