Passengers will have to take buses on the Ballarat line for two weeks from Monday as a construction blitz begins.
A temporary timetable will be available at stations, and passengers should allow at least an extra 45 minutes travel time.
Trains are expected to resume on Monday, July 8.
According to Regional Rail Revival, upgrades include lifting a pedestrian overpass into place and rebuilding the car park at Bacchus Marsh station; building new track at Ballan, Maddingley, Melton, and Caroline Springs; and demolition and rebuilding at Rockbank Station.
Rockbank Station will be closed until August.
Trains between Ballarat and both Maryborough and Ararat will continue, connecting to buses.
Another blitz will begin on August 21, until August 25.
Already, a new pedestrian overpass has been installed at Ballan Station, and upgrade work is also underway at Wendouree Station.
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