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IRVINE, Orange County, Calif., Sept. 29, 2026 — A chain reaction crash involving multiple vehicles shut down lanes on northbound I-405 near MacArthur Boulevard on Monday night, September 28, according to the California Highway Patrol. At least one person reported injuries, though the extent was not released.
The crash was first reported as a two-vehicle collision shortly before 8:45 p.m., with one vehicle striking the right shoulder wall, according to the California Highway Patrol. Additional vehicles became involved within minutes, and radio traffic described what may have grown into a five-vehicle collision. A gray Audi Q5 was reportedly involved in a collision with three more vehicles, and a gray Toyota RAV4 was also reported in a separate collision with a white vehicle and another unidentified car.
By 8:51 p.m., all lanes on the northbound 405 were stopped. A white Hyundai Ioniq 6 and a red Hyundai Elantra were among the vehicles left along the roadway, with the Elantra's driver reportedly declining medical treatment at the scene. One vehicle remained in the number three lane for a time before it was moved.
Three tow trucks were requested to clear the scene, dispatch logs show, as crews worked to remove a red sedan with major front-end damage, a Toyota RAV4 with moderate rear damage, and a Hyundai Ioniq 6 with major front-end damage. No fatalities were reported. The California Highway Patrol has not released a cause for the initial collision, and the incident remains under investigation.
We hope those who were hurt recover fully and quickly.
A Common Misconception About Multi-Vehicle Freeway Pileups
Many drivers assume that chain reaction crashes happen because a driver was going too fast. Speed plays a role in some of these crashes, but the bigger factor is often what happens after the initial impact: drivers behind the initial collision have only a few seconds to react to stopped or slowed traffic, especially at night or where visibility is limited by an overpass or by a lack of lighting.
According to the National Highway Traffic Safety Administration, 28,595 large-truck occupants were injured in multi-vehicle crashes involving large trucks in 2023. That figure is a reminder that the vehicles most often blamed in these events, whether trucks or passenger cars, are frequently just one part of a much larger sequence of impacts rather than the sole cause.
The assumption that a single reckless driver is responsible also oversimplifies how investigators actually work these crashes. In reality, a chain reaction usually involves several separate decisions, from following distance to reaction time, each of which contributes to the outcome.
Frequently Asked Questions
How does fog or low visibility contribute to pile-ups?
Reduced visibility, whether from fog, darkness, or glare, shortens the time drivers have to see a slowdown ahead and react. This is a major factor in multi-vehicle crashes, particularly on freeways where speeds are higher.
Why is following distance so important?
Leaving enough space between vehicles gives drivers time to brake safely if traffic ahead stops suddenly. Tailgating is one of the most common contributing factors to rear-end and chain-reaction crashes.
Are secondary crashes common after an initial wreck?
Yes. Once a crash blocks lanes, approaching traffic often has little warning, which can lead to additional collisions before emergency crews arrive and the lanes are closed off.
What makes multi-vehicle crashes hard to investigate?
With several vehicles and drivers involved, investigators must piece together the order of impacts, who struck whom, and what each driver saw and did in the seconds before the collision.
What to Do After a Multi-Vehicle Crash in Irvine, CA
If you're involved in a multi-vehicle crash, try to move to a safe area if your car is drivable and it's safe to do so, and turn on hazard lights to warn oncoming traffic. Call 911 even if injuries seem minor, since some injuries, especially from secondary impacts, aren't immediately obvious.
Get checked by a medical professional as soon as possible, even if you feel fine at the scene. Exchange information with other drivers when it's safe, and take photos of vehicle positions and damage if you're able to. Request a copy of the official crash report from the California Highway Patrol once it's available, since it can help clarify what happened once the investigation is complete.
