Two carriages of the TranzAlpine scenic train separated by about one metre while pulling into Arthur’s Pass Station due to a broken coupler component, a Transport Accident Investigation Commission report has found.
The report, released yesterday, said the separation on December 17, 2023, was discovered as a crew member walked between the carriages, which were used for luggage storage and a kitchen. Only crew were authorised in these areas, and no one was injured.
Earlier that day, shortly after departing Christchurch, the train’s second front locomotive suffered a fault, causing a “sudden jolt and temporary loss of power”, the report said.
The faulty unit was isolated, and the train continued to Greymouth with one working locomotive.
On the return trip, two extra locomotives were added at Otira to help power the train through the steep Otira Tunnel, which rises 250m over 8.5 kilometres.
A new crew also boarded at this point. While descending into Arthur’s Pass, the engineer applied several brakes and reduced throttle, which led to a coupler component with a pre-existing, undetected fracture breaking.
“It is virtually certain that the train’s configuration of four locomotives operating in throttle position three while applying the train’s brakes to their full capability caused the weakened coupler component to break,” the TAIC report found.
Coincidentally, when the engineer went to disconnect the two front assisting locomotives, they lifted air pressure levers that unintentionally prevented a brake pressure drop from triggering an alert to train control.
The parting caused “significant damage” to the carriage chassis and coupler connection.
A crew member discovered the parting when they went to move between the two carriages, alerting other staff and making a recovery plan to move the parted portions of the train back to Christchurch separately.
The Transport Accident Investigation Commission identified inadequate inspection and maintenance of carriage-coupler connections and the train alarm system failing to alert the crew of the parting, as key safety issues in its report.
In a statement to 1News, KiwiRail said the incident had been treated seriously even though no one had been injured and only crew were authorised to enter the carriages which parted
Chief operations officer Paul Ashton said changes were made to the way the state-owned enterprise operates because of the incident.
“Those changes include improved eye bolts in the coupling system, which are now being installed. At the same time, we will complete a review of the train alarm system and introduce improvements to it by the end of the year to ensure onboard crew are properly alerted when an incident occurs.”
Train inspection regimes have been changed and the operating procedure if a train parted has been being updated, he added.