SAN DIEGO -- Five years and a few days ago, former Gov. Gray Davis stood on a hill overlooking Sorrento Valley before a gathering of dignitaries on an overcast day to kick off a $176 million face-lift of San Diego County's busiest interchange.

Today, regional and state officials plan to gather again on one of the new features of the rebuilt merge between interstates 5 and 805 -- a southbound bypass -- to celebrate the massive project's completion.

Commuters and truckers will get the opportunity to try out the new bypass as it opens to traffic early next week, said Edward Cartagena, a spokesman for the California Department of Transportation in San Diego. A bypass opened on the northbound side a year ago.

Joe Kellejian, a Solana Beach councilman and former transportation chairman for the San Diego Association of Governments, a planning agency, called the project a first step toward unlocking the frustrating congestion on I-5 through North County.

"To me, this improvement, and the improvements on I-15, were the real beginnings of a movement to keep San Diego moving," Kellejian said. "This is going to go a long way toward relieving congestion in this area."

Cartagena said motorists should notice some immediate easing in their commute through Sorrento Valley. At the same time, he said, additional improvements will be required to open up bottlenecks farther north in Del Mar, Solana Beach and Encinitas.

Cartagena said Caltrans plans to launch a project in 2009 to extend car-pool lanes north to Harbor Drive in Oceanside, in an undertaking that could be completed by 2016 if funding is available.

But, for now, Caltrans is focused on celebrating one of the region's largest, most complicated projects in recent memory.

"We're pretty excited about it," Cartagena said.

Essentially, Caltrans built a bypass system that will move people around the merge on barrier-separated, four-lane roadways on either side of the mainline freeway. Both 2-mile-long bypasses will run between the merge and Highway 56 in the San Dieguito River Valley.

In conjunction with next week's debut of the southbound bypass, new southbound onramps and offramps will open at Carmel Mountain Road, Cartagena said.

With the bypasses, the merge will be 22 lanes across.

With an average daily traffic volume of 266,000 cars, the 5/805 merge is the busiest interchange in San Diego County and one of the most congested in Southern California, he said.

By comparison, Cartagena said, the complex interchange of interstates 5 and 10 and highways 60 and 101 east of downtown Los Angeles moves 287,000 vehicles per day and the Interstates 10 and 405 interchange in west Los Angeles handles 281,000. The "Y" merge of interstates 5 and 405 in Orange County handles 200,000 cars, he said.

Besides being a critical link for commuter traffic traveling between residential areas of North County and job-rich Sorrento Valley, the 5/805 merge is a key spoke in a freight transportation wheel that connects Mexico and San Diego County with the twin ports of Los Angeles and Long Beach.

Truckers, Cartagena said, should benefit as much as anyone.

Truck drivers headed south toward the border will be able to keep right, hop on the southbound bypass and move south on I-805 without making the difficult and dangerous lane changes required now, he said.

"That's going to take some getting used to," said Richard Robinson of Oceanside, who drives trucks part time. "But it sounds like a fairly good idea."

It has to be better than what truckers face now, Robinson said.

"You have to move over two or three lanes if you're going to go on 805," he said. "And when you're merging to the left to go on 805, you're fighting with all the people who are merging to the right to go on 5."

Jim Waldorf of Encinitas said he is hopeful the improvements will ease his drive to San Diego Padres baseball games on Friday nights but is more concerned about future projects north of the merge.

"I'm just looking forward to them widening 5 and getting rid of some of these bottlenecks, such as Via de la Valle," he said.

Contact staff writer Dave Downey at (760) 740-5442 or ddowney@nctimes.com. Comment at nctimes.com.