On Tuesday 9 March 1999, Train 523, a southbound New Plymouth to Palmerston North express freight, overran Whangaehu without a valid track warrant and continued approximately 18 km into the next section before the error was realised. There was no opposing traffic or obstruction and once the overrun was discovered a valid warrant was issued and a relief locomotive engineer completed the remainder of the journey. The overrun resulted from a lapse in concentration by the locomotive engineer.
