A Wellington passenger train that derailed and crashed into a concrete block earlier this year, injuring six people, passed a red light signal before being diverted onto a runaway track, an interim investigation has found.
The Transport Accident Investigation Comission (TAIC) today released its preliminary findings into the June 6 crash near Khandallah Station on the Johnsonville Line.
The two-car Metlink train was travelling south towards Wellington when it struck a large concrete block at 33km/h, causing significant damage.
Both crew members on the train were taken to hospital, while four of the eight passengers on board suffered minor injuries. Buckled seats and extensive damage were visible inside the train carriage after the crash.
According to the TAIC's findings, the train was diverted onto a runaway line after a signalling system detected the track ahead was occupied, but it failed to stop before hitting the concrete block.
TAIC chief investigator of accidents Louise Cook said investigators were still working to establish why the signalling system detected that the track ahead was occupied.
"We are still verifying evidence and pursuing several wider lines of inquiry including why the red danger signal was passed," Cook said.
The TAIC is appealing for witnesses after a Metlink train derailed on the Johnsonville Line on Saturday, injuring six people and leaving the line closed indefinitely. (Source: 1News)
Warnings appeared before crash
The interim report revealed the signalling system had detected a possible track occupancy issue earlier that evening, while the train was travelling north towards Johnsonville.
At about 6.50pm, the system registered what was known as a "dropped track", causing it to interpret a section of railway as occupied.
This prompted the system to detect what appeared to be multiple trains in the same section of track, generating an error message on the train controller's screen.
The warning remained visible for 25 seconds but did not trigger an audible alarm to alert the controller.
Although the message disappeared when the train entered Khandallah Station, the system continued to register the section of track south of the station as occupied by another train.
As a result, signals controlling access to that section of track remained red, and the track automatically set to divert approaching trains onto the runaway line.
The passenger train continued to Johnsonville before beginning its return journey towards Wellington at about 6.58pm. It arrived back at Khandallah Station seven minutes later.
Safety system failed to activate
At about 7.05pm, the train manager checked passengers were clear of the doors before signalling that the train was ready to depart Khandallah station to Box Hill station.
A green light and audible alarm in the driver's cab confirmed the doors were closed and the train manager had given the go-ahead to leave.
As the train left the platform, it passed the red signal at around 7.06pm and was diverted onto the runaway line, triggering the emergency brakes.
Despite the emergency brakes being activated, the train continued.
Two seconds later, it passed a trackside safety device designed to automatically apply the brakes if a train passed a stop signal. However, the train's trip lever, which was supposed to activate the braking system, failed to engage.
The train then lost power when it disconnected from the overhead lines, before crashing into a concrete block at the end of the track at 33km/h.
According to the TAIC's report, no emergency alert was received by train control following the collision.
Instead, passengers and nearby residents contacted emergency services, who subsequently notified train control of the crash.
Investigation remains ongoing - TAIC
The crash prompted the closure of the Johnsonville Line, with replacement buses brought in while investigators and recovery crews worked at the scene.
Investigators examined the crash site and gathered evidence including the train's onboard data recorder, signalling logs, CCTV footage and train control communications.
TAIC said its investigation remained ongoing, with further evidence being examined to establish the circumstances and causes of the crash.
A final report would be released later, outlining the commission's findings and recommendations.
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