Sydneysiders are being promised more train services during peak hours under an $880 million plan to upgrade the network's old signalling technology - but not for a few years, at least.
Commuters in the city's south and along the airport line are set to benefit first from the investment, to be allocated over four years in next week's state budget.
The changes will allow trains to run closer together - providing five extra services an hour during peak on the Illawarra line from Cronulla, and eight more an hour at the international, domestic, Mascot and Green Square stations.
The new digital signalling and train control systems - used in the likes of Paris and London - will be rolled out in stages, but they won't start coming online until the early 2020s.
Sydney Trains boss Howard Collins conceded it "will take some time" before the benefits are realised, but the technology has proven to boost capacity to deal with the huge growth in passengers.
Mr Collins believes it has the ability to run trains every 90 seconds, although that's not yet needed in Sydney.
"I think this is as important as the great invention of the double-decker train in Australia, which happened in 1964," he told reporters on Sunday.
"This technology is going to move us forward another generation."
"This is the only way forward for our network."
NSW Premier Gladys Berejiklian labelled it a significant investment that will take the network to a "different level".
"We understand how important it is for people to be able to move around freely, to be able to get to work on time, and to spend less time travelling," she said.
Labor leader Luke Foley labelled the announcement "farcical".
"This will need hundreds of more drivers, trained and employed, and the government hasn't committed to that," he told reporters.
"They can't even run the current timetable because they have too few drivers."