At approximately 2215 hours on Tuesday 24 August 1999, northbound Train 474 struck a derailed wagon while passing southbound Train 227 between Te Rapa and Horotiu on the North Island Main Trunk line. The incident occurred when a UK wagon conveying a 40-foot container on Train 227 became derailed shortly after passing through Horotiu as a result of a tyre working loose on a wheel. The wagon continued in a derailed state, obstructing the parallel up main line as Train 474 approached. The derailed wagon and container struck the locomotive of Train 474 as it passed, damaging the front side of the locomotive and the cab side window. No injuries were sustained.
The safety issues identified were the susceptibility of tyred wheels to loosening due to excessive heat, and the potential consequences of derailed wagons on double line track.
