A 4-mile stretch of the 405 will be shut down between Valley View Street and the 605 Freeway from Saturday at 9 p.m. until Sunday at 5 p.m.
The stretch of the 405 Freeway is considered one of the busiest in the country: an average of 370,000 vehicles travel through each day.
But starting Saturday at 9 p.m., the 405 will shut down completely between the 605 Freeway and Valley View Street in Westminster.
The 20-hour closure, dubbed "Bridge Bash," will have crews demolishing the old bridge linking the southbound 405 Freeway to the eastbound 22 Freeway.
"It's not quite 'Carmageddon,' but sort of like 'Carmageddon,' and we want to get this done as quickly and expeditiously as possible," said Orange County Supervisor John Moorlach.
The construction is part of a $277-million West County Connectors Project spanning 6 miles and passing through six cities. It's expected to be finished by late 2014 or early 2015. Officials say it will ease congestion by connecting carpool lanes on the 405, 605 and the 22.
"This will allow drivers to stay in those carpool lanes from the 405, 22, 605 and not have to weave and merge through there," said Darrell Johnson, chief executive officer of the Orange County Transportation Authority.
Authorities urge people to avoid the area this weekend until the demolition and cleanup is finished by 5 p.m. Sunday.
"If you do have to drive please just make the appropriate plans and be sure to allocate extra time," said Moorlach.