(John McDonnell/The Post)

The highways may be a bit more crowded than usual as travelers head to distant destinations, perhaps via local airports. Be sure to check below for the Metrorail work schedule, as well as for some important developments on several road construction projects.

Metro weekend delays

Travelers beginning their holiday getaways at the airports in the D.C. region will want to note the impact of the Metrorail maintenance program, which will affect service on the Blue, Yellow, Red and Orange lines from 10 p.m. Friday through the midnight closing on Sunday.

Blue/Yellow lines: Free shuttle buses will replace trains between Pentagon City and King Street. The Crystal City, Reagan National Airport and Braddock Road stations will be closed.

Blue Line trains will operate about every 20 minutes between Franconia-Springfield and King Street and between Pentagon City and Largo Town Center.

Yellow Line trains will operate about every 20 minutes between Huntington and King Street and between Pentagon City and Mount Vernon Square.

The last northbound Yellow Line train from Huntington will leave 46 minutes earlier than usual at 1:48 a.m. on Saturday and Sunday — that’s the Friday and Saturday night owl service — and at 10:48 p.m. Sunday. The last northbound Blue Line train from Franconia-Springfield will leave 41 minutes earlier than usual, at 1:48 a.m. Saturday and Sunday, and at 10:48 p.m. Sunday.

Shuttle buses: Some riders are particularly concerned about the impact on travel to National Airport. The transit authority says that the weekend before Thanksgiving is not particularly busy for Metrorail at National. There won’t be any service disruptions from Monday through the Sunday after Thanksgiving, which is a busy time.

During this weekend, Metro is going to operate four shuttle bus routes.

Downtown Express: Non-stop between Metro Center at 12th and G streets NW) and the airport.

Airport Route 1: Between King Street and the airport.

Airport Route 2: Between Pentagon City, Crystal City and the airport.

Local Route: Between Pentagon City, Crystal City, Braddock Road and King Street. This one will not stop at the airport.

At National, the buses stop outside Door 1 (Terminal B) on the arrivals roadway. This is just outside the Alaska Airlines ticket counter.

Riders traveling through the work zone should allow about a half hour for extra travel time, Metro says.

Blue Line: Trains will share a track between Stadium-Armory and Addison Road while crews repair the slabs under the rails. Allow about 20 extra minutes for travel through the work zone.

Red Line: Trains will share one track between Dupont Circle and Judiciary Square stations as crews continue the lengthy project to stabilize the overhead pipes at Farragut North.

From 9:30 a.m. to 9:30 p.m. Saturday and Sunday, trains will leave the ends of the line at Shady Grove and Glenmont about every 10 minutes. Every other train from Shady Grove will terminate at Dupont Circle, and every other train from Glenmont will terminate at Union Station.

At all other times, trains will leave Shady Grove and Glenmont about every 20 minutes.

Trains in each direction will go through the downtown work zone about every 20 minutes.

The last train from Glenmont station will leave 11 minutes earlier than usual, at 2:26 a.m. Saturday and Sunday — the Friday and Saturday night owl service — and at 11:26 p.m. Sunday.

Allow about half an hour extra for travel time, and expect crowding on Metro’s most heavily used line.

Orange Line: Trains will share a track between Ballston and East Falls Church while crews install new track. The trains will leave the ends of the line about every 20 minutes. Add about 20 minutes extra for getting through the work zone.

Beltway/Dulles Toll Road ramp

The Virginia Department of Transportation is planning work this weekend that will restore the second lane on the ramp leading from the eastbound Dulles Toll Road to the Capital Beltway’s inner loop.

The second lane was taken away over the summer as part of the high-occupancy toll lanes project, and that has contributed to the extra congestion that thousands of commuters experience in the work zone north of Tysons Corner.

Weekend work: Before the second lane on the ramp can be opened, crews still must do some prep work. It’s scheduled to start at 9:30 p.m. Friday and continue till 7 a.m. Saturday. During that time, all exits from the eastbound Dulles Toll Road to the Beltway north and south will be closed. If bad weather forces cancellation of this work, the plan is to reschedule it to begin at 9:30 p.m. Saturday.

Detour: Toll Road drivers should continue east to southbound Chain Bridge Road (Route 123), turn right at the traffic signal and follow signs back to the Beltway (I-495 north or south).

Silver Spring parade

The annual parade is scheduled to start at 10 a.m. Saturday on Ellsworth Drive in downtown Silver Spring, then turn south on Georgia Avenue and end at Silver Spring Avenue. See a pdf map.

There’s plenty of weekend parking in Silver Spring garages and the Metrorail station on the Red Line is just a few blocks from Georgia Avenue. It’s best not to park too close to the route. There will be extra congestion on the nearby streets because of the pedestrian traffic and because lanes will be closed on Georgia Avenue during the parade.

George Washington Parkway

The two northbound lanes of the George Washington Parkway are scheduled to close again this weekend, from about 500 feet north of the Spout Run Parkway exit to Chain Bridge Road (Route 123). The closing is scheduled to start at 6 a.m. Saturday and continue till 10 p.m. Sunday, while crews work on stabilizing the rocks along the parkway.

All drivers will have to exit the parkway at Spout Run. They can return to the parkway at Chain Bridge Road.

Another such closing may be needed on the weekend of Dec. 3-4. On weekdays, a single lane may be closed between 9:30 a.m. and 2:30 p.m.

FedEx on Sunday

The Redskins play the Dallas Cowboys at 1 p.m. Sunday at FedEx Field, just off the Capital Beltway in Landover. That usually generates extra traffic around the Beltway exits at Landover Road, Arena Drive and Central Avenue.

The nearest Metro station is Morgan Boulevard, on the Blue Line, a little less than a mile south of the stadium.

Megabus moved

Megabus, the intercity bus service, has relocated its bus bays to the remodeled bus deck inside Union Station’s garage. This is part of the redevelopment of that garage level into a D.C. hub for intercity buses.

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