405 hits breaking point with relief still far off. (Up Front).

The 405 has hit the wall.

Completed in 1964, when L.A.'s population had barely eclipsed 2.5 million, the San Diego Freeway was expected to handle traffic demands for a generation.

But a nearly 20-mile stretch of the 405 between LAX and the Valley maxed out earlier this year, reaching its capacity of 2,000 vehicles per lane per hour as expansion took a backseat to new road development and seismic retrofitting of bridges.

The California Department of Transportation found the traffic breakdown point affected the southbound stretch of the 405 between the Ventura (101) Freeway and Los Angeles International Airport for much of the day.

None of this will surprise motorists who regularly find themselves in stop-and-go traffic between 6 a.m. and 10 a.m. or between 2 p.m. and 10 p.m., well past the periods when northbound lanes along the same stretch moves along at relatively high speeds. The congestion has become tortuous on the weekends as well, when beach traffic has created near-gridlock conditions on Saturday and Sunday afternoons.

"We have more people trying to use the facility than the facility can accommodate," said Frank Kuon, deputy director of operations for Caltrans District 7, which covers L.A. and Ventura counties. "We're experiencing congestion that has spread to mid-day peaks. Any type of incident could impact the system so there would not be any down time in between the peak periods."

Of course, traffic congestion in L.A. is hardly limited to the San Diego Freeway. Just last month, the Texas Transportation Institute, in its annual traffic mobility study, concluded that Los Angeles-area motorists spent an average of 136 hours in rush-hour congestion in 2000, an increase of two hours from the previous year. That was enough to brand L.A. as the nation's most traffic-clogged region -- for the 15th year in a row.

Economists attributed the increase to the exodus of Bay Area technology sector refugees seeking greener pastures in the most stable L.A. base and the overall diversity of well-paying jobs locally.

"If you have a two-earner household, this is the best place in California to be where both partners can find the best employment opportunities," said Jack Kyser, chief economist for the Los Angeles County Economic Development Corp. "Things are not good in the Bay Area, Oregon or Washington so you see a lot of people coming down here. Based on the number of out-of-state license plates I see on the freeways, you're going to see continued strong population growth."

But even by L.A. standards, the 405 is a disaster area for much of the week. With the population of Los Angeles County now exceeding 9.8 million, hundreds of thousands of motorists use the 405 daily as they converge on the Westside from the San Fernando Valley and South Bay.

The hardest hit stretch comes between Century Boulevard near LAX and the Century (105) Freeway. The four regular lanes average 160,000 vehicles per day, including more than 10,000 during the peak hour, exceeding capacity by 25 percent.

The southbound approach to the Santa Monica (10) Freeway ranks a close second, handling 155,000 vehicles daily, including as many as 10,000 per hour over five lanes.

Gridlock hits as two of the five lanes veer off to steer motorists onto the I-10 on-ramp. That creates massive bottlenecking north of the interchange as three lanes are left to carry as many as 9,500 vehicles per hour -- nearly 60 percent greater than the freeway's capacity.

"People in the outer lanes are trying to weave back into the main traffic so they are not forced to get on the off-ramp," said Naresh Amatya, a lead regional planner for the Southern California Association of Governments. "The weaver has to slow down so the traffic behind him slows down. That can cause a chain reaction and it doesn't take a long time for that chain reaction to affect a long stretch of freeway."

Unlike other portions of L.A., alternatives are limited for southbound motorists driving over the Sepulveda Pass. There are a few circuitous routes, along with Sepulveda Boulevard. But mostly, it's the 405. "There's no grid system as you're going over the mountain," said Kuon.

Projects planned

Relief, while in sight, remains distant. Caltrans has a major improvement project in the planning stages, but it won't be ready before 2008.

The $206.1 million project, funded largely through the state's $5.3 billion Traffic Congestion Relief Program and some Metropolitan Transit Authority funds, would build expansion lanes along an 11.6-mile stretch of the southbound road from Waterford Street (just south of Sunset Boulevard) to the 105 Freeway.

The three-phase project, to be placed out to bid after Caltrans engineers finish the design work, entails:

* Construction of a 2.9-mile car pool lane from Waterford Street to the 10 Freeway interchange, as well as separate auxiliary lanes between the Waterford Street, Wilshire Boulevard, Santa Monica Boulevard and Pico/Olympic Boulevard exits. The $47.5 million project will break ground in 2004 and be completed in late 2006.

* Car pool lanes in each direction on the 3.6-mile stretch from the I-10 interchange to the Marina (90) Freeway. The $127.8 million project will commence in early 2004 and is to be complete in the fall 2008.

* Carpool lanes in both directions along the 5.1-mile stretch between the Marina and the Glenn Anderson freeways. The $30.8 million project will begin this fall and is scheduled for completion in spring 2006.

The cost projections include purchasing rights-of-way, many of which will be acquired by eminent domain, Caltrans officials acknowledged.

"There will be times where it is necessary for us to take properties to accomplish the improvements," said Kuon.

He added that road construction would only take place during non-peak periods, which on the 405 would mean a lot of the work would take place between midnight and 5 a.m.

There are signs that these projects can reduce gridlock. A car-pool lane between the 101 Freeway and Waterford Street that just opened has shaved as much as 20 minutes off driving time during peak traffic times for motorists using the lane. It resulted in some time saving in the mixed lanes as well.

But with the car pool and auxiliary lanes south of Waterford Street years from completion, some of the benefits disappear with the car pool lane as users find themselves immersed in the weaving traffic of the mixed lanes.