The driver of a train that crashed in Lower Hutt two months ago tested positive for cannabis use.
The Transport Accident investigation Commission today released its interim findings into the crash at Melling Station on May 27 when a Tranz Metro passenger train overshot the end of the line.
The incident prompted the commission to issue a raft of urgent safety recommendations today.
Deputy chief commissioner Helen Cull QC said the driver, who has more than 11 years' experience, returned a positive drug test after the crash.
The level of cannabis in his system was consistent with a non-chronic user smoking a cigarette two or three days earlier, although it is not clear exactly when the drug was taken.
Cull said the commission was still looking into whether the driver had driven trains two or three days earlier and whether he had failed drugs tests in the past.
It was also looking at potentially slippery conditions, the performance of the train's brakes and the adequacy of driver training provided by KiwiRail as possible factors in the crash.
The incident caused significant damage to a Matangi train and stop block at Melling Station as well the overhead electricity wires that were brought down.
Two of the 12 people on board the train suffered minor injuries.
Cull said the commission had voiced its concern a number of times in the past about transport operators using drugs and she would be worried if the trend continued.
''We have made that an important recommendation that we are putting on our watch-list to be released in the future.''
But she pointed out the driver had already completed three runs that morning and the crash happened on his second trip into Melling Station.
At the time, passengers told The Dominion Post the driver told passengers the brakes weren't working.
Investigator Tim Burfoot said its tests had showed the brakes had the correct air pressure and were responding to the driver's inputs correctly.The wheel-slide protection control valves were also working fine, he said.
But because the brakes were so badly damaged, investigators had not been able to perform a full performance test and could not rule out malfunction.
Cull said the accident happened just as the sun's rays were hitting the track and humidity in the area had reached its peak.
As a result, the commission was looking at whether that humidity could have made the tracks slippery and how effectively Matangi trains stop on a wet or greasy track.
The commission's urgent recommendations to KiwiRail included restricting speeds at Melling Station and similar terminal stations, upgrading stop blocks to better absorb collisions, and shifting any poles carrying overhead wires from behind the end of rail lines.
The commission hopes to wrap up its full investigation by March 2015.
KiwiRail's passenger general manager Deborah Hume said the state-owned rail operator had accepted the commission's findings.
A 25kph speed restriction had since been applied to the Melling and Johnsonville Stations.
The Melling line speed had been reduced from 70kph to 50kph and the stopping distance extended.
''Safety is KiwiRail's main priority and customers and staff can be assured that the company is doing everything to ensure that each journey is a safe one.''
KiwiRail's engineering team was designing a replacement shock absorbing stop block to replace the solid concrete block currently installed at Melling Station, Hume said.
KiwiRail's own investigation was also still under way.
''We both have further work to do to examine wider issues,'' she said.
''The public can be confident that KiwiRail would never operate any of the Matangi or Ganz Mavag services if there were any concerns about performance and safety."
Hume said the driver's positive drugs test was still under consideration by the commission and KiwiRail would not comment on an individual employment matter.
"KiwiRail's comprehensive drug and alcohol policy and programme is in line with international best practice and is compliant with the Australian and New Zealand testing standards."
CONCERNS OVER BRAKES
The Rail and Maritime Transport Union said it had heard ''numerous'' concerns from train drivers about the effectiveness of the Matangi braking system.
General secretary Wayne Butson said a stop-work meeting had been scheduled for today to allow drivers to provide feedback on the problems they have experienced.
He acknowledged the commission had found drugs in the driver's urine but said no conclusions had been drawn from this.
''At this point no allegation of driver impairment has been made, and the RMTU have seen no evidence of driver impairment.''
The union would work with KiwiRail on interim recommendations released by the commission today, he said.
- The Dominion Post