SAN MATEO, San Mateo County, Calif., Sept. 27, 2026 — Multiple vehicles collided on Friday afternoon, September 25, on northbound US-101 near the Hillsdale Boulevard offramp in San Mateo. At least one person was reportedly trapped inside a vehicle, and injuries were reported at the scene.
The California Highway Patrol's incident log describes a chain-reaction crash involving several cars, including a silver Nissan Sentra, a red Tesla, a white Honda CRV, and at least one other silver sedan. Two vehicles reportedly rolled onto their sides during the crash, and a person was said to be trapped inside one of them on the left side, CHP radio traffic indicated.
Officers classified the crash as an injury collision after an ambulance was requested for the scene. A separate vehicle involved was noted as drivable and was not reported to have caused injury. The exact number of people hurt and the extent of their injuries had not been released as of this writing.
The crash blocked the slow lane and partially blocked the off-ramp for a period Friday afternoon, according to CHP dispatch notes, though the roadway status as of this writing is unclear. The California Highway Patrol has not released a cause for the crash, and the incident remains under investigation.
We wish the injured a complete and speedy recovery.
When Rollover Crashes Are Most Likely to Happen
Rollovers tend to cluster around the same conditions that strain a driver's attention and a road's surface. Late afternoon and early evening hours, when commute traffic thickens and drivers are merging, changing lanes, or reacting to sudden slowdowns, see a steady share of these crashes. Wet pavement, sun glare near sunset, and stop-and-go traffic near freeway interchanges and offramps can all make it harder for a driver to correct a sudden skid or swerve before a vehicle tips.
Weekend nights and holiday periods bring a different mix of risk, usually tied to fatigue or impaired driving, but weekday rush hour has its own hazards: dense traffic, frequent lane changes, and drivers merging on and off ramps at speed. A relatively small steering correction or a side-impact hit at the wrong angle can be enough to send a vehicle onto its side or roof, especially where lanes narrow near an interchange.
According to the Insurance Institute for Highway Safety, 24 percent of fatally injured occupants in crashes classified as other, which were mostly rollovers, were belted in 2023. That figure reflects how frequently seat belts are not in use in the crashes where rollover risk turns most serious.
Frequently Asked Questions
Why are rollover crashes so dangerous?
A rollover can throw unbelted occupants against the roof, windows, or each other as the vehicle turns onto its side or roof, and the roof itself can crush inward on impact. The risk of serious injury rises sharply compared with a typical frontal or rear-end crash.
Which vehicles are most prone to rolling over?
Taller, narrower vehicles with a higher center of gravity, such as SUVs, pickup trucks, and vans, are generally more prone to rollovers than low, wide sedans. Vehicle loading, tire condition, and speed also affect how easily a vehicle tips.
Does wearing a seat belt change survival odds in a rollover?
Yes. A seat belt keeps an occupant positioned inside the vehicle's protected space as it rolls, reducing the chance of being thrown against the roof or ejected. Unbelted occupants face far higher odds of serious injury or death in a rollover.
What is a "tripped" rollover?
A tripped rollover happens when a vehicle's tire strikes a curb, guardrail, soft shoulder, or another object that causes it to pitch onto its side or roof, rather than rolling from steering or speed alone. Most rollovers on public roads are tripped rather than caused by high-speed maneuvers alone.
What to Do After a Rollover Crash in San Mateo, CA
If you're involved in a rollover, stay as still as possible and check for injuries before trying to move, especially if you feel pain in your neck or back. Call 911 if it hasn't already been done, and wait for paramedics to help you exit safely if you're trapped or unsure of your injuries.
Once you're clear of immediate danger, seek a medical evaluation even if you feel fine. Adrenaline can mask pain from strained muscles, head impacts, or internal injuries that don't show symptoms right away. Get a copy of the CHP or police report once it's available, and keep records of any medical visits tied to the crash.
