Nine rail lines will be closed for more than three weeks in April to make way for metro tunnel construction.
More than 1.5 million commuters will be hit by the changes - affecting more than 1.5 million Melbourne commuters.
From April 1 to 23, buses will replace trains on the Cranbourne, Pakenham, Frankston, Sandringham, Mernda, Gippsland and Geelong/Warrnambool lines.
All rail lines passing through Richmond station will be shut over the three weeks, except for the Alamein, Belgrave and Lilydale lines. The Glen Waverley line will also be shut on some occasions.
The trains are closed for a constriction blitz of the Metro Tunnel as well as level crossing removal and other rail upgrades.
Passengers will have to allow for up to an hour extra travel time on their commutes.