Construction of a 7-Story Freeway Interchange : The Challenge: Keep Traffic Moving

Even by state standards, the California Department of Transportation field office on Imperial Highway in Inglewood is a dreary place.

Opened eight years ago for the Century Freeway project, the office appears to have been decorated with Caltrans hand-me-downs--ancient metal desks piled high with dusty blueprints.

In the middle of the office, however, sits an 8-by-8-foot model of the massive, $200-million interchange that will be built at the junction of the existing San Diego Freeway and the Century Freeway, now under construction.

With its linguine-like tangle of plastic tunnels and ramps, the model details how the interchange will appear when completed six or so years from now, its five levels arching upwards to the height of a seven-story building.

“Most people are impressed with the tunnels,” said Vorrie Young, who has managed the office since it opened. “In this area we aren’t used to tunnels like they have in Northern California.”

Despite the interchange’s size and complexity, Caltrans officials say the biggest challenge in constructing it will be keeping traffic flowing along the San Diego Freeway and nearby arterials.

Not only is the San Diego one of the most congested freeways in the Los Angeles area--on an average day, traffic along the freeway where it passes Imperial Highway often exceeds 250,000 vehicles--but major boulevards and highways have also become more clogged by commercial development, they say.

To Jack Felker, a retired Caltrans engineer who worked on the interchange’s design for six years, the scenario adds up to a motorist’s nightmare.

“It’s going to be murder, but you can’t make an omelet without breaking an egg,” Felker said. “People are going to be screaming ‘I went that way last night and now there is a detour.’ It’s going to be a terrible traffic hassle until it’s built.”

Caltrans officials do not agree. No serious problems have occurred since construction started, and they say they are confident none will occur in the future, largely by virtue of a giant detour project that calls for the San Diego Freeway to be kept open at all times by splitting it open and circling it around the interchange site.

“I think our engineers have looked at this very thoroughly,” said James McManus, Caltrans’ Century Freeway chief. “And we feel fairly confident that most if not all the issues are resolved.”

Said Paul Askelson, the Caltrans engineer in charge of bridge construction for the Century project: “What you do is build a little piece, and move traffic over, build another little piece, and move traffic over, and so on.”

The Century Freeway will be 17.3 miles long and run from Los Angeles International Airport east to the San Gabriel River Freeway. It will have four lanes in each direction, one of which will be reserved for car pools and high-occupancy vehicles. A light rail line will operate down the middle of the freeway.

Once it is completed--projections now call for work to be finished in 1993--Caltrans officials say congestion on major east-west arterials in the South Bay near the new freeway should ease. Traffic planners estimate the Century will carry 180,000 vehicles daily near its junction with the San Diego Freeway.

The interchange itself is expected to be the single most expensive construction project along the entire Century route, edging out the Harbor and Century freeways interchange by about $20 million. It is also expected to generate millions of dollars in income to the state as Caltrans leases out airspace rights around it. The term airspace refers to the state-owned land next to, above or under a freeway.

Construction on the interchange, one of four along the Century route, has been underway since January, 1984. Caltrans engineer Norm Taylor said eight contracts already have been awarded to widen bridges, move utility and sewer lines, realign La Cienega Boulevard and build frontage roads.

Taylor said that while work on the interchange progresses, other construction crews will work on the first leg of the Century Freeway expected to be completed--a viaduct stretching from the San Diego Freeway over Imperial Highway west to Sepulveda Boulevard on Los Angeles airport property. The one-mile stretch is expected to be completed by 1990, he said.

Felker said the final design of the interchange was decided upon after two others were tossed out as less practical. One of the designs called for the intersection to built higher, while the other called for it it to be “stuck down in the ground,” he said.

Engineers also believed that because land in the area is so expensive, the interchange should be designed to maximize the amount of airspace that could be leased, Felker said. In all, about 20 acres are expected to be available when the structure is completed.

Roger Williams, who oversees the Caltrans airspace leasing program in the Los Angeles area, said that preliminary estimates indicate the agency could earn $4.5 million by 1995 in gross revenues from airspace leased near the interchange. If an annual inflation rate of 5% is taken into account, the amount could total $64.5 million in 55 years--the number of years tenants who sign airspace leases are typically bound to, he said.

Thus far, Caltrans says few problems have cropped up in keeping traffic flowing in the area. Despite some complaints about noise and dust, and inquiries from some aerospace industry employees in the area about detours, work has progressed smoothly--a view shared by some working in the area.

“They have been remarkably efficient in not disrupting traffic during commuter hours,” said airport spokeswoman Virginia Black.

But as construction accelerates, additional traffic in the area will undoubtedly be generated by the work crews themselves, Caltrans officials said. And periodic lane closures and detours will become more frequent.

Freeway to Stay Open

Whenever possible, Caltrans said it hopes to confine such inconveniences both on the San Diego Freeway and adjacent streets to the nighttime when traffic should not be as heavy. And the San Diego Freeway, which experiences few “off peak” hours, will never be shut down, they say.

Starting next spring, work is expected to begin on a $16 million detour project that will skirt the San Diego Freeway around the interchange construction site. The detour, like the present freeway, will be four lanes in each direction and will be about a mile in length.

Taylor said the detour--the longest of any detour along the Century route--is expected to remain in use for two or three years. The detour was necessary to allow construction crews to build three tunnels, one of which will run under La Cienega Boulevard and the other two under the San Diego Freeway. The tunnels will allow traffic on the Century to link up with the San Diego.

Ed Nahabedian, a Caltrans traffic engineer, said that while it is “hard to imagine what will happen” when construction reaches its peak, the agency is hopeful that its efforts to synchronize signal lights on major arterials such as Imperial will help.

Additionally, such steps as posting signs advising people of alternate routes should assist in keeping traffic flowing in the construction area, he said.