Three northbound lanes on Interstate 405 shut down for at least 30 minutes Thursday morning after two cars overturned near Santa Monica Boulevard in West Los Angeles, the California Highway Patrol reported. CHP issued a SigAlert shortly after 8 a.m. covering lanes 4, 5, and 6, then extended the alert for an additional 30 minutes at approximately 8:30 a.m. At least one person at the scene declined transport to a hospital; whether anyone suffered serious injuries was not immediately clear.
SigAlert timeline
| Time | Event |
|---|---|
| Before 7:30 a.m. | Crash reported to CHP near Santa Monica Boulevard, West Los Angeles |
| Shortly after 8 a.m. | SigAlert issued; northbound I-405 lanes 4, 5, and 6 closed |
| Approximately 8:30 a.m. | SigAlert extended an additional 30 minutes |
| Later Thursday morning | All affected lanes cleared and reopened |
The closure pulled three consecutive lanes from the northbound side as emergency crews worked to clear the wreckage through the height of the morning rush.
SigAlert policy and trigger
Under CHP policy, a SigAlert is issued when an unplanned event is expected to delay a large number of motorists for at least 30 minutes. Qualifying situations include traffic collisions, spilled loads, flooding, and unexpected congestion. Thursday's two-car rollover, blocking three lanes at peak hour, met the threshold. The agency extended the designation once by 30 minutes before crews cleared the scene.
Traffic impact and alternate routing
KTLA video showed traffic stacking behind the crash site as some drivers caught in the growing backup attempted to exit the freeway. The collision occurred on northbound I-405 near Santa Monica Boulevard; the freeway continues north from the Westwood area toward the Sepulveda Pass.
Caltrans has previously directed northbound motorists departing Santa Monica Boulevard to travel east to Sepulveda Boulevard, then continue north to an I-405 entrance at Moraga Drive.
Cause and investigation status
The cause of the crash was not immediately determined, and CHP had not announced any citations or arrests as of Thursday morning. Fox News Digital contacted the California Highway Patrol for additional information and received no response by publication time. All affected lanes were eventually cleared and reopened.