Metro is opening an hour early Saturday to help accommodate runners heading to the Navy-Air Force Half Marathon and Navy 5 Miler.
The Metrorail system will open at 6 a.m. Saturday.
Metro says the Smithsonian station is the closest one to the starting line of the race. But the transit agency warns that two stations on the Blue and Yellow line will be closed due to scheduled reconstruction.
Beginning at 10 p.m. Friday, buses will replace trains between Braddock Road and Pentagon City. The Reagan National Airport and Crystal City stations will be closed.
Work is also scheduled on the Red, Green and Orange lines.
Normal operations will resume Monday morning.
