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

How will traffic be affected?

Some downtown streets already are closed to vehicles, and more, including Arlington Memorial Bridge, will close by Friday, New Year's Eve, to accommodate activities on or near the Mall (see map). Times and locations of street closings may change on short notice. Officials strongly recommend you take public transportation if you are coming downtown.

What if I still decide to drive?

Parking will be banned in large sections of downtown. Some parking garages will close Friday, so check first. If you are lucky enough to find street parking, it will be free because Friday is a federal and a District government holiday.

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--will run from 11 a.m. to midnight Friday along Constitution Avenue between 10th and 14th streets NW.

The Ronald Reagan Building and International Trade Center will open to the public at 6 p.m. Friday 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 starts at the Lincoln Memorial at 9 p.m. Friday and runs until about 1 a.m. The free show will be hosted by actor Will Smith and will feature a variety of entertainers and, 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. There will be fireworks at the Washington Monument at midnight, with the display visible from much of the downtown area.

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

Metro trains will begin running at 8 a.m. Friday and will be in service until 3 a.m. Saturday. 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.

Metro will provide free shuttle bus service near the Mall from 1 a.m. until all 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.

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

All tickets to the Smithsonian special millennium programs in three of its auditoriums have been reserved. But no-shows usually average from 15 percent to 25 percent, according to Smithsonian officials, so last-minute openings are possible. The programs start at 11:30 a.m. Friday 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.

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

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

You cannot drink or possess open containers of alcohol on National Park Service property or city streets. However, limited amounts of alcohol will be sold at the District's millennium celebration on Constitution Avenue.

Will events be canceled if there is bad weather?

No. The National Weather Service is forecasting temperatures in the mid-50s during the day Friday, with lows in the mid-30s. There's a chance of light showers, but they are supposed to end by evening. Damp or cold weather will not force cancellation of the show at the Lincoln Memorial, and the District's celebration on Constitution Avenue has 60,000 square feet of space in heated tents.

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.

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.

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. The District's street festival will continue on Constitution Avenue from 11 a.m. to 6 p.m. And the Smithsonian special millennium programs will continue Saturday and Sunday, beginning at 11:30 a.m., at the three museum auditoriums.

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

Officials say it is unlikely that there will be major problems because of the Y2K computer glitch. They suggest preparing the way you would 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.

Get extra supplies for infants, the elderly or others with special needs. Have enough cash for a long weekend, but don't get too much because of the risk of theft. Have at least a half-tank of gas in the car. Keep up-to-date medical and financial records. Don't fall for Y2K scams. For example, do not give out your credit card or Social Security number to someone unless you initiate the call.

What about my cat, dog and fish tank?

Plan ahead in case you have to leave your house. Most emergency shelters will not accept pets, according to the Humane Society, although some hotels will. Keep extra pet supplies on hand. And don't forget that some pets get spooked by fireworks, so make sure they are safely confined when the celebration begins.

Where can I get more Y2K information?

The Washington Post is printing a complete list of local Y2K emergency numbers and other information in this week's Weeklies and Extras. In addition, there are links to local governments on The Post's Web site at www.washingtonpost.com. Also, starting Friday, the federal government's Y2K information line (1-888-872-4925) will operate 24 hours a day.

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. In the event of widespread, prolonged power outages, many local governments will open emergency shelters in schools and fire stations. In the District and many suburbs, emergency sites will be set up in different communities to reach police, firefighters and others if the telephone lines don't work.

Road Closings

Below are the street closings for the District up to Friday. A more complete guide to street closings, including Friday and Saturday closings, will appear later in the week.

1. Constitution Avenue between 9th and 14th (until 11 p.m. Jan. 2.).

Today

2. 12th Street Tunnel northbound (from 1 p.m. to 11p.m. on Jan. 2)

3. 12th Street between Independence and Pennsylvania (from 1 p.m. to 11p.m. on Jan. 2).

Tomorrow:

4. Tenth and 11th streets, NW, between Constitution and Pennsylvania avenues (from 12:01 a.m. to 7 a.m. on Jan. 2).

* Henry Bacon Drive between Lincoln Circle and Constitution Ave. (from 9 a.m. to 6 a.m. on Jan. 1). NOT SHOWN ON MAP.