With just hours to go until the arrival of Carmageddon in Los Angeles, we thought it was worth going over the details for those of us who will be watching from the other side of the country.

What’s happening?

A 10-mile stretch of Intertstate 405 in Los Angeles (also known as part of the San Diego Freeway) will be closed this weekend to allow for demolition work on the Mulholland Bridge. Here’s a map of the project, and there’s a handy countdown clock available on the Los Angeles Department of Transportation’s traffic site.

How bad will this be?

Nobody really knows for sure. The roadway carries an estimated 500,000 vehicles over a typical weekend. Officials are worried about a domino effect causing major problems on other major arteries, so they’re urging people to stick close to home and avoid long trips (or avoid driving at all, if possible).

When will it end?

Everything is scheduled to reopen by 6 a.m. on Monday, though it could open earlier if work is finished ahead of schedule.

Why do we care about this in Washington?

Because while our traffic is generally a nightmare, this looks like it could cause unusually epic and far-reaching congestion. They don’t add the “-ageddon” or “-pocalypse” suffix to just anything, do they? And transportation planners will be studying what happens to see what lessons can be learned from the shutdown.

Couldn’t this wind up being much ado about nothing? Isn’t it possible the media is over-hyping this?

Come on, when has the media ever over-hyped anything? And if this winds up petering out and not having the expected effect (see: Y2K), public officials will presumably point out that their dire warnings kept people off the road and that averted the problem.

I’ve never been to Los Angeles. What’s the closest local comparison you can make?

You know how the Capital Beltway is one of the worst freeways in the United States? Imagine if, for one weekend, officials closed the Beltway, a bunch of the Metro stations and, just for fun, a handful of bus routes. Something like that. (We may be exaggerating, but not by that much.)

You know that if everyone biked everywhere, this wouldn’t even be an issue, right?

We wanted to make sure the bicycle crowd was not ignored. (Unlike the Los Angeles Police Department, which won’t allow for bicycle rides on the freeway during the closure, due to safety concerns.)

What have officials said and done to try and avoid having major traffic issues on roads in the area?

Mayor Antonio Villaraigosa urged drivers to nix “all unnecessary auto trips” to help reduce congestion on the region’s roadways. “If you think the 405 is gridlocked during the week, you haven’t seen anything yet,” he told the New York Times. “My message is to stay home. Or go on vacation. Walk. Go on a bike. But do not get in your car and go anywhere near the West Side. It’s going to be a mess.”

To counter the expected traffic debacle, local officials are turning to other transit options. The Los Angeles County Metropolitan Transportation Authority will be adding 100 buses and 32 rail cars this weekend, increasing service along some bus and train sections and letting people ride for free on certain routes.

Yeah, but this has to do with Los Angeles, so what is the celebrity angle?

The Los Angeles Police Department asked celebrities with large Twitter followings to help get the word out. Ashton Kutcher, Demi Moore, William Shatner and Kim Kardashian all pitched in, as did Tom Hanks.

How can we keep up with the news over the weekend?

Your best bet will be following the #carmageddon on Twitter, though a lot of that will presumably be people complaining that traffic kept them from seeing the new “Harry Potter” movie. The project overseeing the construction will be tweeting all weekend (@I-405.). You can also follow the project on Facebook. There will also be live images of the demolition work available here.

If the Beltway ever closes for a weekend, will Ashton Kutcher tweet about it?

We can only hope.