LOS ANGELES >> The alarms have been sounded and the preparations have been made.

Now, only two questions remain: Will "Carmageddon," the shutdown of a 10-mile stretch of one of the busiest highways in the United States, on one of the city’s busiest of summer weekends, bring the City of the Angels to its knees?

Or will this too come to pass, just like so many other predictions of the apocalypse? (Remember the Oakland radio preacher who just last spring put up billboards promising the world would end on May 21.)

"Like Y2K," Ashley Nazarian said dismissively, referring to the much-hyped worldwide computer data meltdown that never happened as the clock turned to Jan. 1, 2000.

Nazarian, property manager for the Sherman Oaks Galleria, a mall that is located next to an exit on the affected stretch of the 405, might be worried but she isn’t.

Word that part of the freeway will be shut down for 53 hours beginning at midnight Friday has been spread so far and wide by now that she believes people will stay away.

Still, the UCLA Health System, which runs the huge Santa Monica-UCLA Medical Center, is taking no chances.

It has three helicopter companies on standby to transport patients and human organs in the event of emergency operations. It is laying in extra medical supplies and 5,200 boxed lunches for its staff.

Dr. Wally Ghurabi will be sleeping in the hospital’s emergency room over the weekend rather than try to commute the 20 miles from his home to the hospital, located blocks from the 405.

"You can’t take a chance when you deal with patient safety and patient care," he said.

Authorities, meanwhile, have been preparing the public for the closure for weeks. Signs on freeways as far away as San Francisco have been flashing the same message over and over: Stay off the 405 July 16-17. On Thursday, Facebook said it will direct about 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.

Numerous celebrities, including Tom Hanks, Piers Morgan and Maroon Five’s Adam Levine have joined the cause, taking to Twitter to get the message out.

William Shatner, who as Capt. Kirk of "Star Trek" traveled in space where no man had gone before, indicated on Friday that he won’t be going anywhere near the 405.

"LA friends, the 405 closes this weekend in what surely will be Carmageddon," Shatner tweeted.

Then, with a few more characters to burn before he reached Twitter’s 140 limit, added a plug for his forthcoming "Star Trek" documentary, "The Captains."

Transportation experts said Friday 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.

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.

"Otherwise we’ll have a low-key time out in Long Beach," she said of where they’ll be staying with their niece. "I guess there’s stuff to do out in Long Beach."

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. Movie theaters along the 405 are giving away popcorn.

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.