A train wagon accidentally shunted into Picton Harbour prompted a three-day, $500,000 recovery effort, a report says.

Nobody was injured in the incident, which happened on the afternoon of September 1, 2021.

A Transport Accident and Investigation Commission report into the shunting was released today.

It said a shunt locomotive at the Picton freight yard was in the process of relocating a single wagon when the incident happened. The shunt was being operated by remote control, with the operator wearing the control pack in a harness on their chest.

“The remote-controlled shunt locomotive and single attached wagon travelled onto the rail linkspan before entering the harbour at the Picton ferry terminal. It was an unintended shunting movement. At the time of the incident there was no ferry berthed at the wharf and the rail linkspan was not in use,” the report said.

The shunt and wagon travelled 112m at 3km/h while the operator was facing away from them, listening to a conversation on the UHF radio. By the time the operator turned around, the shunt and wagon were already on the rail linkspan, which is designed to connect the rail ferry Aratere to the rail line at the ferry terminal.

Port Marlborough responded quickly with spill-containment equipment and absorbent booms to keep the environmental impact to a minimum. Two empty containers inside the wagon provided enough buoyancy to help keep it afloat.

The 52-tonne locomotive and the wagon were recovered using two 300-tonne cranes. The salvage operation took three days and cost more than $500,000.

“Unintended rail movements in any situation are serious incidents with potentially serious consequences. On this occasion, a shunt locomotive crossed an unprotected road crossing before entering the rail linkspan at Picton and entering Picton Harbour. Fortunately, the road crossing was not occupied at the time and there were no personnel working on the rail linkspan,” the report said.

The commission found the unplanned and unintended movement of the shunt locomotive caused the overshoot into the harbour, but said there was “no single factor that led to this incident”.

The shunt and wagon travelled up the rail linkspan before falling into the harbour. Photo / Supplied

“Instead, it is very likely that a combination of factors contributed to the unintended movement.”

However, it did find the operator was likely distracted, and their attention was “switching between multiple task demands in an effort to achieve all the required tasks efficiently prior to their shift handover”.

There was also nothing on the remote-control pack to warn the operator what was happening.

The operator was also working independently instead of with a team, which was the usual process, and KiwiRail’s rules did not cover when an operator should deactivate a remote-control operator pack to prevent unintended movements.

The report also noted the rail linkspan was not protected from rail movements when it was not in use.

People in a two-person shunt team should maintain visual contact where possible to mitigate risks, the report said.

“Periods of busy activity, even if they are not cognitively demanding, can present challenges. Organisations should be mindful of such challenges and ensure workers are well equipped with strategies to manage workflow, and have measures in place to ensure workers are able to remain focused on safety-critical tasks.”