Crews removed the final cones on the freeway bridge at 6 a.m. Officials have planned a ceremony for later in the day to celebrate the opening.
The old bridge was built in 1959 and had to be demolished as part of the I-405 Sepulveda Pass Improvements Project. The new bridge spans 608 feet and is 10 feet wider than the old bridge.
"It's been a lot of patience for the people who live in this area, and we really thank them for that," said Paul Gonzales of Metro. "This bridge is now a world-class bridge. It's longer, it's wider, it's more seismically safe, and most importantly, it has room underneath it for the carpool lanes being constructed."
A 10-mile stretch of the 405 Freeway was shut down for an entire weekend in the summer of 2011 due to construction. In an effort to warn drivers of possibly unprecedented gridlock, officials dubbed the closure "Carmageddon."
But the weekend of construction went by smoothly without major traffic tie-ups, as most motorists stayed away from the area.
In 2012, a similar shutdown occurred for the other half of the bridge that spans I-405, with similar smooth results.
The entire $1 billion project is expected to be completed by the middle of next year.
The Associated Press contributed to this report.