Sydney commuters will be faced with more train delays this week, despite the union flagging a potential "breakthrough" in negotiations.
The Rail, Tram and Bus Union (RTBU) has stepped up its industrial action, which has been ongoing since the end of last year, stemming from concerns around the new intercity train fleet.
They claim the trains present safety risks, and have been seeking guarantees that guards will continue to be used.
Emerging from the union's stop-work meeting at the Blacktown Workers Club this afternoon, RTBU Secretary Alex Claassens said progress was imminent.
"Unless another minister interferes with that process, we may actually be able to come out and say, sometime tomorrow afternoon or in the next few days, that there'll be a breakthrough on the deed," he said.
"We've been fighting the safety of the new intercity fleet for over six years, we've been trying to get them to commit to a document that's in writing."
Union members walked off the job this morning, causing major disruption across the network.
Rail workers officially went on strike between 10am and 4pm — but Sydney Trains warned commuters to expect disruption on either side of that.
It will impact the Western, North Shore, Olympic Park, Northern and Cumberland lines.
One commuter at Blacktown Station said the protracted industrial action was frustrating.
"It's been crazy to be honest, it's really disrupted a lot of us that are travelling on a day-to-day basis," she said.
"I had to take a bus just to get here and have to wait an hour for my next connection.
"We'll just hang tight but it's been an inconvenience for the past few months."
Another had taken time off work to avoid the disruption.
"It's annoying, I've taken a lot more leave than what I normally would because of it."
The union will return to the negotiating table at 10am on Wednesday but extensive strike activity planned on Thursday is still likely to go ahead.
"I think Thursday's too far gone, I think we've already got all the planning in place," Mr Claassens said.
He emphasised that once the deed regarding the intercity fleet had been signed, talks over a new enterprise agreement would continue.
"Even if magically, everybody agrees to the deed overnight, it's still going to go through a process," he said.
"Once the safety issue is addressed, yes, we are going to stand up for good wages and conditions."
NSW Treasurer Matt Kean said $1 billion had been put "on the table to meet the union demands with regard to the new trains".
"We have agreed to meet the union demands to rip out safety equipment like CCTV cameras, and sensor technology," Mr Kean said.
"And the union said if we met those demands, put the money on the table which we have done, they would stop the strikes.
"Well, they haven't stopped the strikes and just this morning, thousands of school kids are late to school. Their parents are late to work. Small businesses are suffering because of the industrial warfare being waged by (Opposition Leader) Chris Minns and his mates in the union movement and it's got to stop."
In the meantime, Sydney Trains chief executive, Matt Longland, said commuters should avoid all unnecessary travel for the next few days.
"Unfortunately, commuters will experience longer journey times, less frequent services, and changes to stopping patterns due to this industrial action," he said.
"We are working closely with the Rail, Tram, and Bus Union to put an end to the daily delays and cancellations on the train network and minimise the ongoing impact to our customers."
At this stage, all suburban trains will run to an amended timetable on Thursday with an extensive reduction in services during peak periods.
