Transport officials in the NSW government were warned a year ago that parts of the digital trains radio system that crashed last week were outdated, a confidential document reveals. The entire Sydney train network shut down last Wednesday, stranding tens of thousands of afternoon peak-hour commuters. It took more than an hour for trains to resume running after the digital radio system that signallers and train controllers use to stay in contact with crews failed. The report by Transport for NSW, which is dated March 24 last year, found that components in the digital trains radio system were “obsolete”. “This has been identified as a priority, with funding reallocated to address this and staff training also being considered as a long-term mitigation measure,” the report said.