At about 1121on 17 June 2010, a safeworking irregularity involving CityRail passenger service SN57 and train D231, a Pacific National light engine, occurred at Moss Vale in New South Wales. On the day of the occurrence, planned maintenance on the Argyle Street bridge, (southern end of Moss Vale) was being conducted in accordance with ARTC's SAFE Notice 2-1334/2010. By way of the SAFE Notice, the Australian Rail Track Corporation (ARTC) had promulgated that Down CityRail services would be routed from the Down Main via 140 points set reverse (an unsignalled movement) then terminate alongside the Moss Vale Up Platform before forming the return Up service to Campbelltown.

The investigation determined that the network controller, in error, gave the driver of CityRail passenger train SN57 verbal authority to pass signals MV15 and MV39 in the Stop position, over 140 points set reverse, to access the Up Platform at Moss Vale. A little earlier, the controller had authorised train D231 to travel into the Moss Vale Up Refuge Siding, also over 140 points, thereby placing the two trains into direct conflict.

Fortunately the network controller recognised the error and stopped train D231 about 200 m before 140 points, the potential point of conflict. There were no injuries or damage to rolling stock or infrastructure as a result of the incident.

The investigation established that an error by the network controller was the main factor contributing to the incident. However, the ATSB considers that the use of a checklist or similar systemic defence measure by network controllers for this type of working may enhance the integrity of ARTC's current safeworking arrangements.