Inner Sydney train stations including Central, Town Hall and Circular Quay will be shut down over the weekend for trackwork.
RailCorp says major cleaning work will take place at Redfern, Central, Town Hall, Wynyard, Circular Quay, St James and Museum stations on February 9 and 10.
RailCorp will also complete infrastructure upgrades including the installation of new track, signals and overhead wiring.
Buses will replace trains on the City Circle and Airport lines, while other lines have been modified.
Commuters are urged to allow for extra travel time and to check CityRail's website for information.