KiwiRail admits it hasn't made the final payment on the latest Chinese made locomotives it bought last year, because they haven't met their performance target.
Since 2009, KiwiRail has bought 63 of the D L-class engines In the past year none of the engines met KiwRail's own performance target of 80,000 kilometres between any faults that cause a delay of 15 minutes or more.
That includes the 15 new Generation 2.3 D L locomotives, which were only introduced in the first half of last year.
KiwiRail's chief operating officer Todd Moyle told RNZ reporter Catherine Hutton that wasn't unusual as they were working through teething problems, which is typical with new engines.
