A week after the Sydney train network was shut down during the afternoon peak it has been revealed NSW Transport officials were warned a year ago that communication components on trains were old and could fail.

A confidential report by Transport for NSW 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, stranding thousands of passengers for more than an hour and causing major delays.

Sydney Trains said it identified in 2021 that parts of the Digital Train Radio System (DTRS) would become “obsolete” in the next five years.

Plans were being made for a broader technology upgrade of train radio systems based on the 5G spectrum, while relying on the old system until the changes could be made.

“The DTRS has been operating reliably across the rail network in Sydney since 2016 and the system is upgraded regularly,” a Sydney Trains spokeswoman said.

“Transport for NSW and Sydney Trains are working together on a plan for the broader technology upgrade for train radio systems, while continuing to keep the current system operating reliably.”

Despite battling ongoing industrial action, adverse weather events and the impact of COVID-19, Sydney Trains says it has prioritised an extensive maintenance program across the network.

Around $1.4 billion is slated to be spent conducting maintenance this financial year, with $800 million already spent.

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.

Premier Dominic Perrottet called the outage a “freak incident”.

“These incidents happen from time to time, they do,” he said.

“Transport did everything they could to get it back on and up and running as soon as they could – and they did in a little over an hour.”

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 analogue hand-held radios as a backup in case communications are temporarily severed again.

The Sydney trains spokeswoman said analogue radio is an approved alternate communication platform within the organisation’s network rules.

“It is not uncommon for analogue radio to be used as an additional backup option,” she said.

An internal investigation into the system failure is ongoing.

– AAP