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SOUTH SAN FRANCISCO, San Mateo County, Calif., Nov. 13, 2026 — A chain reaction crash involving several vehicles shut down lanes on southbound US-101 on Wednesday evening, November 11, just south of Sierra Point Parkway.
The California Highway Patrol said the crash was first reported shortly before 5:30 p.m. as a collision between a dark colored sedan and at least one other vehicle. Within minutes, dispatch logs show the incident had grown to involve three vehicles, and later reports put the count at as many as four. One vehicle, described as a blue sedan, was reportedly struck from both sides, and radio traffic noted smoke or steam coming from one of the involved cars.
A person who called in the crash was in a blue sedan and was not hurt. The extent of injuries to others involved was not detailed in the available dispatch information. The California Highway Patrol upgraded the call from an unknown-injury collision to one with injuries and medical response en route, and a SigAlert was issued for the southbound lanes, with two of the lanes blocked and long delays expected. Caltrans crews were called in to help clear the scene, and officers at one point said they intended to stop all lanes briefly to move the vehicles out of traffic.
Officials have not released further details on what led to the initial collision or whether speed or any other factor played a role. The crash remains under investigation.
We hope those who were hurt recover fully and quickly.
More Crash News from San Mateo County
This multi-vehicle crash happened on US-101 in South San Francisco, CA. For other recent crashes near South San Francisco, CA, visit our San Mateo County accident news page.
Frequently Asked Questions
Are secondary crashes common after an initial wreck?
Yes. When a first crash blocks lanes, traffic stacks up quickly, and drivers approaching the backup may not slow in time, leading to additional collisions in the same spot.
What makes multi-vehicle crashes hard to investigate?
With several vehicles involved and drivers usually describing events differently, investigators typically rely on vehicle damage patterns, lane position, and traffic camera footage to piece together the order of impacts.
What usually causes chain-reaction pile-ups on highways?
These crashes commonly start with one vehicle stopping or slowing suddenly, usually due to an earlier incident, congestion, or a hazard on the road, with following vehicles unable to stop in time.
