The impact of a construction blitz will be tested this morning with no trains between the city and Caulfield.
Affected sections of the Frankston, Cranbourne and Pakenham lines will have replacement buses all week.
Works started on the weekend but today those heading to work are being told to allow extra time to ensure they get to their destination.
The shutdown will allow for an upgrade of power, signalling and communications in preparation for the Metro Tunnel.
Tents have sprung up across the network to shelter commuters, and with showers forecast all week, it’s likely to be a damp trip.
Roads will also be busier than usual, with delays expected on the Monash Freeway, Nepean Highway and Princes Highway.