The southbound San Diego Freeway (405) will be closed Tuesday and Wednesday night from the Ventura Freeway to Getty Center Drive.
Crews are scheduled to install frame structures for the Skirball bridge in the Sepulveda Pass.
Freeway ramps will be closed on the southbound side of the 405 as early as 7 p.m. Tuesday, with some lane closures beginning around 10 p.m.
All southbound lanes on the 405 between the 101 Ventura Freeway and Getty Center Drive will be shut down from midnight to about 5 a.m. Wednesday.
The northbound side will close too - but on Thursday and Friday nights.
The Los Angeles County Metropolitan Transportation Authority said the Skirball bridge will be closed the rest of the week, between 10 p.m. and 6 a.m.
The alternate route is Sepulveda Blvd.
Metro offers frequent updates on the Sepulveda Pass Improvement Project via Twitter @I_405.
View I-405, Skirball Bridge Closures: June 18-June in a larger map