A confidential report by Transport for NSW published on Monday in the Sydney Morning Herald warned trains' digital radio system components were obsolete and fixing the problem was a priority.
The Sydney rail network's digital radio system, which controls communication between trains and the rail operations centre failed at 2.45pm last Wednesday.
The breakdown stranded 250,000 commuters trying to get home, causing a ripple effect across the city's transport system as buses quickly filled up and chaos ensued.
Every Sydney train was parked for 90 minutes, awaiting instructions before getting the all-clear just after 4pm.
Train drivers are reportedly going to get hand-held radios as a backup in case the technology fails again temporarily severed.
Labor's transport spokeswoman Jo Haylen said Sydney Trains most recent maintenance backlog for the 2021-22 year was $670 million.
"Passengers simply want a safe and reliable public transport system," she said.
"The Liberal government was warned a year ago that components in the Digital Train Radio System were already obsolete.
"They knew that this could put the whole train network at risk but not enough has been done because there is no accountability."
