The northbound San Diego (405) Freeway was shut down at midnight Tuesday, with full closure in the West Los Angeles area expected to last until 5 a.m. Wednesday.
The freeway was closed from the Montana Avenue off-ramp north to the Moraga Drive off-ramp (map).
The closure is needed for workers to pour concrete for the deck of the northern side of the Sunset Boulevard bridge.
The southbound 405 Freeway will be closed for the same reason beginning midnight Thursday and lasting through 5 a.m. Friday.
Portions of Sepulveda Boulevard, Sunset Boulevard and Church Lane will be closed during that timeframe as well. More details on surface street closures are at Metro.net.
Officials are likely to begin closing lanes at about 10 p.m. on the evenings when work is scheduled overnight, including Tuesday. Some freeway on and off ramps may close as early as 7 p.m., according to the Metropolitan Transportation Authority.
Metro is overseeing the massive, $1 billion freeway-widening effort officially known as the I-405 Sepulveda Pass Improvements Project.
As part of the project, a major weekend-long, 53-hour closure of the 405 Freeway – being dubbed "Carmageddon 2" – is slated for Sept. 29 to 30. Signs alerting travelers to that upcoming traffic nightmare went up this past weekend.
NOTE: An earlier version of this story had the incorrect times for the southbound closure, which will begin Thursday night and end Friday morning. The post has been updated.