[This post has been updated]

Metro riders on the Green, Yellow and Orange lines will face major disruptions this weekend as the transit authority takes advantage of a three-day weekend (yes, Monday is a federal holiday, Columbus Day) to shut some stations while workers install new equipment and conduct repairs.

On the Green and Yellow lines the Shaw, U Street and Columbia Heights stations will be closed while workers install new track switches. Free shuttle buses will replace trains between Georgia Avenue and Mount Vernon Square.

On the Orange Line buses will replace trains between East Falls Church and West Falls Church while crews on the Dulles Metrorail project work to link the new line with the Orange Line. Buses will be used to link the stations, which will remain open for transfers.

Customers throughout the weekend should add 20 minutes or more to their travel times as the shuttle buses are not as efficient as trains at moving people from place to place. They carry fewer people and can be delayed by traffic congestion.

That will be of special concern to workers on Monday who don’t have Columbus Day off. Commuters should add extra time for their trips or consider alternate methods of transportation.

Metro suggested that Green Line passengers traveling to and from stations north of Georgia Avenue could avoid the work zone by traveling on the Red Line, which does not have any track work scheduled for the weekend.

There is one bright spot: On Sunday Metrorail will open an hour early — at 6 a.m. — to accommodate crowds for the Army 10-Miler. The free buses shuttling passengers around closed rail stations will also begin service at 6 a.m.