WASHINGTON -- Metro is telling Blue, Orange, and Silver line riders to "only take Metro if you have no other option" for two weeks this month.

The transit agency is handing out flyers and tweeting alerts about track work that will slash service on the Orange and Silver lines by at least half. Trains along the entirety of the east-west rail arteries will be slowed to 20 minutes.

The 16-day slowdown begins Saturday, August 11 and continues until August 26. Metro said ridership is lighter in August.

"The project is needed to address the tightest curve in the Metrorail system between McPherson Square and Smithsonian stations," said a Metro news release.

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To keep trains moving, crews will spend one week rebuilding one side of track and the next week rebuilding the other. Metro said workers will install new rail and fasteners as well as repair concrete pads that support rails.

Even still, Metro warns this will mean "extensive crowding and delays."

The work also means no Blue line trains between Rosslyn and Arlington Cemetery. Riders traveling between Virginia and downtown D.C. should use the Yellow Line, said Metro.

A Metro spokesman said the work was first announced in February and was in the works even longer.

You can read Metro's full alert by clicking here.