Heading out for New Year's Eve celebrations? Have concerns about possible Y2K computer glitches? Here are answers to some frequently asked questions. For a guide to all major millennium events, see today's Weekend section.

Q: How will traffic be affected?

Many downtown streets are closed today to accommodate activities on or near the Mall, and more will close during the fireworks. Times and locations of street closings may change on short notice. Officials strongly recommend you take public transportation to get downtown.

Q: What if I still decide to drive?

Parking is banned today in large sections of downtown, and some parking garages will close. But if you find street parking, it will be free because today is a federal and a District government holiday.

Q: I am coming from Virginia, and I have to drive. Help!

The Arlington Memorial Bridge will be closed from 11:30 a.m. today until early tomorrow, as will Washington Boulevard between the bridge and Interstate 395. The Roosevelt Bridge will close about midnight tonight for an hour. The 14th Street Bridge is open but isn't recommended because adjacent streets are closing. Don't use the bridge unless you are headed to the Southeast-Southwest Freeway. The American Legion Bridge, Chain Bridge, Key Bridge and Woodrow Wilson Bridge will be open.

SmarTraveler advises allowing an hour to get across the bridges to go home after the fireworks, just as on the Fourth of July.

Q: When do the millennium events begin?

The District's celebration -- Main Street Millennium, a street fair with free music and food and drink for sale -- runs from 11 a.m. to midnight along Constitution Avenue from 10th to 14th streets NW.

The Ronald Reagan Building and International Trade Center will open to the public at 6 p.m. for a Millennium Around the World celebration of dance and music from many countries. The program will run until 2 a.m.

America's Millennium Gala will start at the Lincoln Memorial at 9 p.m. and will run until about 1 a.m. The free show will be hosted by actor Will Smith and feature a variety of entertainers and, at about 11:40 p.m., a special 18-minute film by Steven Spielberg. The memorial grounds will open to the public at 6 p.m., with access limited to four entrances (see map in Weekend), but more exits will open after the show, especially along Constitution Avenue. There will be fireworks at the Washington Monument at midnight, and another burst at 12:52 a.m., with the display visible from much of the downtown area. There will be limited food and beverage sales on the Mall.

Q: If I take Metro, what do I need to know?

Metro trains begin running at 5:30 a.m. and will be in service until 3 a.m. tomorrow. Officials say that trains will run at least every six minutes after midnight but that they cannot forecast travel times. Buses will run on a Saturday schedule until 4 a.m.

Parking is free at Metro-operated lots, but rides will not be free. Metro officials suggest buying a round-trip Farecard in advance. Bicycles will not be allowed on Metro trains today.

Metro will provide free shuttle bus service near the Mall from 1 a.m. until the crowds have cleared. The shuttles will depart from Independence Avenue and Ohio Drive, just south of the Lincoln Memorial, to the Rosslyn, Waterfront and Pentagon stations, and from 20th Street and Constitution Avenue, west of the Ellipse, to the Farragut North and Farragut West stations.

Q: What if I want to see one of the millennium programs at the Smithsonian?

All tickets to the Smithsonian's special millennium programs in three of its auditoriums have been reserved. But Smithsonian officials say no-shows usually run about 15 percent to 25 percent, so last-minute openings are possible. The programs will start at 11:30 a.m. at the National Museum of Natural History, and at noon at the National Museum of American History and the Hirshhorn Museum. All seats will be filled 10 minutes before each event.

Even if you can't get into these special programs, the Smithsonian museums will be open from 10 a.m. to 5:30 p.m.

Q: This is New Year's Eve -- what are the rules about alcohol?

You cannot drink or possess alcohol -- even unopened cans or bottles -- on National Park Service land, including the Mall, George Washington Memorial Parkway, Fort Washington or Rock Creek Park. On city streets, you cannot drink or possess open containers of alcohol. However, limited amounts of alcohol will be sold at the District's millennium celebration on Constitution Avenue.

Q: Will events be canceled if there is bad weather?

No. And the forecast is good -- a midnight temperature in the mid- to upper 30s, with no precipitation predicted today, according to the National Weather Service. The District's celebration on Constitution Avenue has 60,000 square feet of space in heated tents.

Q: Where do I go if I get sick or lose a child?

There will be six first-aid tents between the Washington Monument and the Lincoln Memorial, and six tents at the District's Constitution Avenue celebration, as well as areas for lost children.

Q: What if I want to stay home?

The show at the Lincoln Memorial will be broadcast live on CBS-TV, starting at 10 p.m.

Q: What's going on downtown on New Year's Day?

The Millennium Around the World program will continue at the Ronald Reagan Building, starting at 6 a.m. tomorrow. The District's street festival will continue on Constitution Avenue from 11 a.m. to 6 p.m. And the Smithsonian millennium programs will continue tomorrow and Sunday, beginning at 11:30 a.m., with all museums open as usual.

Q: What preparations should I make in case something goes wrong with Y2K?

Officials say it's unlikely there will be major problems because of the Y2K computer glitch, but they suggest preparing as for any long holiday weekend or major snowstorm. Have on hand at least three days' worth of bottled water, either store-bought or from the tap, and ready-to-eat food that doesn't need cooking, plus flashlights, batteries, a battery-operated radio, warm blankets and a first-aid kit.

Remember to get extra supplies for your pets and to keep them safely confined during fireworks. For more information, there are links to local governments on The Washington Post's Web site, www.washingtonpost.com. Also, starting today, the federal government's Y2K information line (1-888-872-4925) will operate 24 hours a day.

Q: What if something does go wrong -- all the traffic lights go out, or the whole area loses power?

If traffic lights go out, treat intersections like four-way stops, but watch for cross-traffic that may not stop. If there are widespread, prolonged power outages, many local governments will open emergency shelters; if telephone lines do not work, they will open walk-in sites to reach police, firefighters and others.