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DIAMOND BAR, Los Angeles County, Calif., Oct. 5, 2026 — A multi-vehicle crash blocked the connector from northbound State Route 57 to eastbound State Route 60 early Sunday morning, October 4, according to the California Highway Patrol. The wreck involved at least a silver Honda Civic and a gray Tesla Model 3, among other vehicles, the agency reported.
The California Highway Patrol said the collision was first reported just before 1 a.m., with a caller stating one or more vehicles were stopped and blocking lanes on the transition road. A person involved in the crash told dispatchers the vehicles involved had their lights off at the time, and one vehicle was later found blocking a lane with hazard lights on and reportedly undrivable.
Los Angeles County Fire Department units responded to the scene. The connector from northbound 57 to eastbound 60 was shut down for a period overnight while crews worked the scene, and tow trucks were called to clear the roadway. The transition lane reopened by around 1:21 a.m., per CHP updates.
Investigators continue reviewing the crash. We hope those who were hurt recover fully.
Why Multi-Vehicle Pileups Turn So Severe So Fast
A crash on a freeway interchange rarely stays a two-car problem for long. Once a vehicle stops or slows in a travel lane, especially on a transition road with limited sightlines and higher approach speeds, every vehicle behind it is closing distance fast. The difference between a near-miss and a secondary impact often comes down to a second or two of reaction time.
Weight and speed differences matter as much as the number of vehicles involved. A compact sedan struck from behind by a heavier vehicle absorbs force through its rear structure, which is built to crumple and protect the cabin, but that design only works within a narrow range of impact speeds. Beyond that range, protection drops off quickly. Interchange ramps also tend to curve and narrow, which limits how far drivers can see a stopped vehicle ahead until they are already on top of it.
The more dangerous phase of many pileups isn't the first impact, it's what happens after. Drivers who stop in a live lane, get out to check damage, or wait for help are exposed to oncoming traffic that may not see them in time. Fire crews and tow operators working a blocked lane face the same risk, which is why agencies routinely shut down a full lane or ramp rather than leave responders working next to moving traffic.
Frequently Asked Questions
Why does fog or low visibility make multi-vehicle pileups more likely?
Reduced visibility shortens the distance a driver has to spot a hazard and react. On ramps and interchanges, where sightlines already curve, fog or darkness can turn a stopped vehicle into a hazard that other drivers encounter with almost no warning.
Why does following distance matter so much in these crashes?
A longer following distance gives a driver more time to brake or steer around trouble ahead. On interchange ramps, where speeds and curves combine, a few extra car lengths can be the difference between stopping safely and rear-ending a stopped vehicle.
Are secondary crashes common after an initial wreck?
Yes. Once a vehicle is disabled in a travel lane, the risk of a second collision rises until the scene is cleared or protected. This is why agencies often close full lanes rather than leave a single lane open around a crash site.
What makes a multi-vehicle crash hard to investigate?
Investigators have to reconstruct the order of impacts, determine which vehicle struck which, and account for conflicting driver accounts, all while working from damage patterns and witness statements instead of firsthand observation of the crash itself.
What to Do After a Multi-Vehicle Crash in Diamond Bar, CA
If you're involved in or come upon a multi-vehicle crash, try to move your vehicle out of a live travel lane if it's safe to do so, and turn on hazard lights immediately. Staying inside a disabled vehicle in a travel lane is often safer than standing outside it in the dark.
Call 911 and report the crash's exact location, including the direction of travel and any identifying landmarks, so responders can find it quickly. Even if you feel fine, a medical check is worth getting, since some injuries from a sudden stop or impact don't show symptoms right away. Keep a record of what you observed, including the time and the vehicles involved, in case it's needed later for an official report.
