Train, tram and bus travel will be free for another month across Victoria before fares are then halved until the end of 2026.
Daily Myki fares will be capped at $5.70 from June 1, half the usual daily maximum of $11.40.
The average commuter will save an estimated $850 across the six months, according to government figures.
The measure, announced by Premier Jacinta Allan on Sunday, is designed to relieve pressure at the pump by encouraging commuters to ditch their cars.
It extends Labor's policy of free transport for April, a move Ms Allan acknowledged had made certain services busier than usual.
"I do acknowledge that our regional and our metropolitan trains are busier than they have been because public transport is free," she told reporters on Sunday.
"That, to me, demonstrates that by listening to the Victorian community, by understanding that they are looking to their government for additional help."
Concerns about overcrowding on V/Line services have persisted since the initial month of free travel was announced, escalating during the Easter long weekend.
Asked whether extra services would be added to cope with the demand, Ms Allan insisted the government had been busy upgrading the network in recent years.
"We've added 1200 additional weekly services as a result of opening the Metro tunnel - those services started from February," she said.
"We've got additional services that we announced in last year's budget that are coming online from the middle of this year, and we added hundreds of additional regional services."
The move will cost $432 million in foregone revenue, according to the government, adding to the estimated $70 million price tag for free travel in April.
The cost-of-living relief measures will be key features of the upcoming state budget, to be released in May, and come amid an election year.
Opposition Leader Jess Wilson said the policy was a welcome cost-of-living measure but needed to be accompanied by better safety measures.
Protective service officers will be redeployed from 119 suburban train platforms to focus resources on crime hotspots, Victoria Police said on Saturday.
Ms Wilson said the change would leave commuters more vulnerable to crime at a time when services were busier than usual.
"I think Victorians will be rightly concerned that … the premier is promising to provide free or discounted access to public transport, she's also making public transport less safe," she told reporters on Sunday.
She said the benefits of free transport would not extend to all Victorians, including those who did not live near public transport lines.
The move comes amid global fuel security concerns related to conflict in the Middle East.
A fire at one of Australia's two remaining oil refineries late on Wednesday has also raised questions about domestic fuel security.
The Viva Energy Geelong refinery, southwest of Melbourne, supplies more than half of Victoria's fuel and about 10 per cent nationwide.
The refinery is operating below full capacity but Viva has assured the public consumers will not be impacted.
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