Westbound I-80 Closes Through SoMa October 23 to 26 for Bayshore Viaduct Work

Caltrans will close all lanes of westbound Interstate 80 on the Bayshore Freeway viaduct through SoMa from Friday, October 23 to Monday, October 26, 2026. The closed stretch runs between 5th Street and 15th Street, and the 5th Street off-ramp is the last exit before it, according to Caltrans’ San Francisco freeway projects page.

The SFMTA’s weekly traffic advisory puts the hours at roughly 11 p.m. Friday to 6 a.m. Monday. Caltrans has not yet posted a news release with exact times, so check QuickMap before you drive.

Why It Is Closing

Caltrans lists the closure as joint construction work under its rehabilitation of the Central (US-101) and Bayshore (I-80) viaducts, a two-year project that began in January 2026. The project page describes the scope as polyester deck overlays, new joints, barrier rail repairs and deck repairs on both viaducts. The same project fully closed eastbound I-80 between 17th and 4th streets for about 55 hours in April.

Who Is Affected

Westbound I-80 is the route from the Bay Bridge onto the freeway network toward US-101 south, the Central Freeway and Octavia Boulevard. Caltrans says traffic will be diverted off at the Fremont Street and 5th Street exits. Its detour map sends drivers over surface streets including 9th Street and Harrison Street, and toward Octavia Boulevard. The SFMTA advisory says detours will be posted.

If you are crossing the Bay Bridge into San Francisco that weekend and heading for the Peninsula or SFO, BART runs from the East Bay to the SFO station with no freeway involved. Caltrain runs from 4th and King to Millbrae, where BART connects to the airport.

The SFMTA describes the closed section a little differently, as running from 4th Street to the US-101 and I-80 interchange. The two agencies agree on the dates and on westbound only.

Another 101 Closure Is Coming in November

Caltrans has also added a southbound US-101 full closure through the Hospital Curve for November 6 to 9. The project page says it replaces the October 2 to 5 closure that was originally on the schedule. The Hospital Curve closures began with northbound weekends in September. Southbound I-280 and southbound Potrero Avenue were the listed alternates for the October weekend.

Same Weekend in the North Bay

The I-80 work overlaps with the Highway 37 closure between Vallejo and Sears Point, which shuts both directions from 10 p.m. October 23 to 5 a.m. October 26. Caltrans’ detour for that closure uses SR-121, SR-12 and SR-29. Our October guide has the rest of the month’s closures.

Caltrans posts real-time conditions on QuickMap at quickmap.dot.ca.gov and updates at sfhighwayprojects.com.

Photo: Caltrans.