Coaches will be replacing trains between Waurn Ponds and Wyndham Vale for the next two weeks.
Transport Victoria said passengers using the Geelong line up until Sunday April 13, will need to allow up to 40 minutes extra travel time.
Trains will continue to run between Wyndham Vale and Southern Cross.
Coaches will replace trains on the Warrnambool Line between Warrnambool and Southern Cross during the same time.
Crews will carry out track works in the Geelong tunnel between South Geelong and Geelong stations, landscaping and signal works between South Geelong and Waurn Ponds, level crossing upgrades at Lara and Little River, upgrades to the Warrnambool stabling facility, annual track maintenance and vegetation removal works between Colac and Warrnambool.
Passengers are encouraged to visit ptv.vic.gov.au/disruptions for more information and to plan their journey.
