A recent investigation into a grain train collision near Tamworth, New South Wales, has resulted in a safety advisory being issued to rollingstock operators on the often‑misunderstood functionality of automatic couplers.
On 6 January 2022, three banking locomotives separated from a grain train, and then collided with the rear of the train when it stopped, resulting in substantial damage.
The accident was investigated by the Office of Transport Safety Investigations (OTSI), which investigates rail accidents in New South Wales on the ATSB's behalf.
It found the train separation was highly likely due to the knuckle on the bottom operated coupler of the lead banking locomotive remaining unlocked after coupling.
Coupling of the banking locomotives had taken place earlier in the train's journey at Werris Creek and, notably, it was found a positive stretch test was not performed prior to departure.
"Commonly, a stretch test is performed with a low traction power setting to ensure tensile pressure is placed on the coupler knuckles, to confirm they have locked after coupling," OTSI Acting Chief Investigator Jim Modrouvanos said.
"In this case, the couplers did not lock correctly, and the train separated during transit when it changed from a compressive (bunched) state to a stretched state."
OTSI's investigation noted key personnel involved in the coupling procedure had a misunderstanding of how an aspect of the automatic coupler's safety design features operated.
Subsequently, a safety advisory notice has been issued to rollingstock operators to ensure workers have an understanding of coupler operation.
"Knowledge of the design features of automatic couplers, their differences and limitations, particularly with regards to locking mechanisms, is key to understanding the importance of conducting a positive stretch test at the conclusion of a coupling manoeuvre," Mr Modrouvanos explained.
"Rollingstock operators should ensure their operational staff are advised and assessed on coupler locking design features which assist in maintaining a knuckle in an unlocked state and methods required to ensure the knuckle has again locked after coupling has occurred."
As detailed on the day of the report release, the investigation also led to a second safety advisory notice, focused on competency assessment standards in the rail sector.
