Decades-old trains will remain on the tracks until the mid-2030s to prevent the derailment of a plan for NSW manufacturing, a key plank of the state government's election campaign.
Some $447 million in the upcoming NSW budget will go to extending the life of the Tangara train fleet while the government investigates locally built replacements through a $17.5 million strategic business case.
"This will kickstart our process when it comes to our supply chains, our workforce, to allow us to build the future trains that we need while keeping our services running well," Transport Minister Jo Haylen said on Wednesday.
Sydney Trains staff will complete the upgrades, providing technology and accessibility improvements.
"The same people that will help us refresh these Tangaras ... will help us build their replacements," Ms Haylen said.
"We've built great trains here before and we will do it again."
Supporting local manufacturing in government procurement was a key plank of Labor's 2023 election campaign.
Premier Chris Minns downplayed the pre-budget announcement, suggesting it would attract little interest "unless you're an absolute train nut".
"But it is the kind of investment that makes a massive difference to the public transport system," he said.
"(This investment) is designed to bridge the gap between what we currently have and the next generation of Tangaras to be built right here in NSW."
The premier criticised train procurements brokered by the former coalition government, saying they were subject to delays and cost overruns.
"We'll have the capabilities onshore, we'll be able to make changes to the rolling fleet as it happens," Mr Minns said.
A fleet of new intercity trains, planned to enter service in late 2019, have been sitting idle awaiting modifications after the first sets arrived from Korea.
Spanish-built replacements for interstate and regional trains ordered in 2019 began arriving in February but are yet to enter service.
Opposition transport spokeswoman Natalie Ward said the government would struggle to commission a new, locally made fleet before the next election.
"I'm concerned for a project of this size, politics will be put ahead of proper procurement processes in order for Labor to meet its promise," she said.
The Newcastle-built Tangara trains, which make up a quarter of the Sydney Trains fleet, will be upgraded from 2025.
The trains entered service in 1988 and are the biggest contributors to maintenance faults across the rail network.
The Tangara fleet had its life extended to 2027 before the latest announcement, which could lead to them remaining on the rails until 2036.
Elsewhere, ageing police stations will be upgraded and more funds used to improve technology for investigators under another pre-budget announcement.
The high-tech crime branch of the state's forensic evidence and technical services command will receive $14.2 million over four years after requests for its assistance doubled over the past five years.
The branch assists with telecommunication interceptions, data retrieval and DNA identification.
Police stations at Waverley and Rose Bay, both in Sydney's eastern suburbs, will also be modernised at a cost of $22.9 million.
The NSW budget will be delivered on June 18.
