Despite the apocalyptic warnings blaring from local television — or perhaps because of them — traffic appeared to be lighter than usual on Interstate 405 and other major freeways.

A 10-mile stretch of the 405 connecting the west side of the city with the San Fernando Valley was scheduled to close for 53 hours beginning Friday night.

Around the afternoon rush hour, the city was to activate its emergency operation center before highway officers began blocking access to on- and off-ramps. Freeway lanes were to close one by one until authorities complete a full shutdown by midnight.

Non-emergency street maintenance and repair projects were scheduled to halt. Police, firefighters, paramedics and traffic engineers were on standby to respond to any emergency.

The Fire Department, which last month lost 18 fire companies because of budget cuts, was paying overtime to stage more than two dozen additional engines, fire companies and ambulances in neighborhoods they might have a hard time reaching from jammed roadways.

"Our biggest concern is gridlock, obviously," Battalion Chief Chuck Butler said during a morning news conference. "There are a lot of areas over in West L.A. and the San Fernando Valley that we expect to be impacted due to the closure."

Six aircraft also will be available, including air ambulances.

Luckily, the wildfire threat had not reached its seasonal peak, and the weekend forecast called for higher humidity, Butler said.

"Although we’re always concerned about brushfires, this particular weekend I think Mother Nature is going to give us a break."

For weeks, officials have issued grim warnings about the closure in the same tones reserved for floods and threatening wildfires.

Dan Bernstein, an avid Los Angeles bicyclist, was rolling along Mulholland Drive in Hollywood when he stopped to share some advice at the news conference at a scenic stop overlooking the Hollywood Bowl.

"We are planning to drive slower and allow more time to get anywhere," he said. "Being rushed just creates more chaos and more accidents. So just slow down, enjoy the sights, and if you have a bike, get out and ride it."

To prepare the public for the closure, they flashed signs on freeways as far away as San Francisco reminding drivers over and over: Stay off the 405 July 16-17. They recruited celebrities with large followings on Twitter, such as Ashton Kutcher and Kim Kardashian, to get the message out.

Facebook agreed to direct some 6.6 million driving-age people in the greater Los Angeles area to the Metropolitan Transportation Authority’s Facebook page detailing the latest traffic conditions this weekend.

Transportation experts said the publicity campaign seems to be working.

They now predict that while there will likely be some backups on other freeways and on surface streets near the 405, the weekend shouldn’t end in massive gridlock.

"It’s going to be fine, people had a lot of warning," said Lisa Schweitzer, a professor of urban planning at the University of Southern California.

Experts compared the shutdown to other big planned events, such as the 1984 summer Olympics, Los Angeles Lakers championship parades and Michael Jackson’s memorial service two years ago.

The disastrous traffic jams predicted for each of those events never materialized. People knew to stay off the road. In fact, city residents marveled that, during the two weeks of the Olympics, traffic was actually much lighter than usual.

"For the 1984 Olympics, by repeating how complex and difficult it’s going to be, some people chose not to travel, to take public transit or go away for vacation," said Martin Wachs of the Rand Corp. think tank.

That could be the case again this weekend. Not that some people aren’t still worried, as closing that section of the 405 for such a long time is pretty much unprecedented.

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Judy Feldman of New York and her husband had planned a trip to Southern California long before they learned of the closure. They planned to spend the weekend going into the city.

Now, all she’s been hearing has been one message about their plans: "No, I wouldn’t do that."

Their planned trip to the popular Getty Center museum is out, as it’s located right in the middle of Carmageddon and will simply close down that weekend. So will the nearby Skirball Cultural Center.

"We’ll be glad when Monday is here," said Skirball spokeswoman Mia Carino, who is cautiously optimistic that she’ll be able to drive to work that day.

Feldman and her husband still hope to get to Los Angeles to take in other museums.

Transportation officials say the closure is necessary to replace the 50-year-old Mulholland Bridge as part of a $1 billion project to widen a perpetually bottlenecked segment of the 405.

That stretch goes through the Sepulveda Pass, which connects the San Fernando Valley to Los Angeles’ West Side.

They say a full closure is necessary to demolish one side of the span, and they picked this weekend to minimize impact to traffic on a workday. They expect another closure next year to replace the other half.

On a typical July weekend, about a half-million vehicles use that section to get to such major destinations as Los Angeles International Airport, UCLA, Beverly Hills and numerous popular beaches.

To discourage driving, the city is offering free rides on the subway and certain bus lines and adding more commuter train service. Hotels and restaurants are offering discounts.

Around town, some people are organizing neighborhood walks, bicycle rides and even "Carmageddon" parties.

Joann Killeen, who lives near the 405, is going to attend such a party Saturday at her next-door-neighbor’s house.

"We’re going in our garages and looking for old Scrabble boards and Monopoly games and we’re going to bring potlucks and just be silly from about 5 o’clock until midnight," she said.