Passengers in western Sydney are are urged to plan ahead this weekend, as essential Rail Repair Plan trackwork occurs.
Buses will replace trains between Penrith, Richmond and Granville on the T1 Western, T5 Cumberland and Blue Mountains lines.
From 10pm Friday through the weekend, buses will replace trains between Central and Bondi Junction on the T4 Eastern Suburbs Line.
From 7.30pm Saturday to 4.40am Sunday, buses will replace trains between Berowra and Hornsby on the T1 North Shore Line and between Wyong and Hornsby on the Central Coast & Newcastle Line.
Sydney Trains will have more than 800 workers undertaking a significant amount of work to remove around 40 high-priority defects.
Passengers are encouraged to allow extra travel time and plan ahead by visiting transportnsw.info or using trip planning apps.