This weekend, Metro is closing several stations and part of the busy Red Line that runs through the core of downtown.

Beginning at 10 p.m. Friday through midnight Sunday, five stations will be closed: Farragut North, Metro Center, Gallery Place, Judiciary Square and Union Station. Riders can use free shuttle buses provided by Metro to get around those stations.

The Blue and Orange lines will be usable from Metro Center, and the Yellow and Green lines from Gallery Place.

The work is part of Metro’s $5 billion rebuilding plan to fix the ailing 37-year-old rail system.

For two years, the transit agency has been aggressively working on weekends when it has more time to get critical equipment on the tracks and fewer riders on the system. Because equipment and materials must be moved onto the tracks, officials said, there often isn’t enough time in the off-hours, when the system is normally closed, to do the work.

Who will be affected?

This downtown shutdown will probably affect about 150,000 rides, or more than a quarter of weekend passengers, based on an analysis of detailed ridership from Metro statistics.

The closure comes as Metro has seen its ridership drop about 20 percent this week during the federal government’s shutdown, leaving some trains and stations nearly empty in the morning and evening rush hours. As a result, the transit agency is running only six-car trains instead of longer, eight-car trains that can transport more people.

Metro’s rail ridership fell by 9 million trips to 209 million for fiscal 2013, compared with the previous year. Revenue is $20.3 million less than expected.