Tangiwai disaster  The Tangiwai disaster occurred at 10:21 p.m. on 24 December 1953 when the Whangaehu River bridge collapsed beneath Wellington-to-Auckland express passenger train No. 626 at Tangiwai, in the central North Island of New Zealand. The locomotive and first six carriages derailed into the river, killing 151 people. The subsequent Board of Inquiry found that the accident was caused by the collapse of the tephra dam holding back nearby Mount Ruapehu's crater lake, creating a large lahar in the Whangaehu River, which destroyed one of the bridge piers at Tangiwai only minutes before the train reached the bridge. The disaster remains New Zealand's worst rail accident. On 24 December 1953 the 3 pm express from Wellington to Auckland consisted of a KA class steam locomotive hauling 11 carriages: five second class, four first class, a guard's van and a postal van. With 285 passengers and crew, the train was stated by a witness—the station agent at Tangiwai railway station—to have passed through Tangiwai Station on time at 10:20 pm at about . The specified maximum track speed between Hihitahi (to the south of Tangiwai) and Ohakune (to the north) at the time was . There was no evidence presented to the Board of Inquiry regarding any calculations made or indications of the speed of locomotive 949 either as it approached the incident site or at the time of the incident. Approaching the bridge over the Whangaehu River at Tangiwai, in response either to Cyril Ellis, a passerby, standing by the track and waving a torch or on seeing the condition of the bridge, the driver (Charles Parker – Locomotive Engineer First Class) shut off steam and initiated an emergency air brake application, while his fireman (Lance Redman) shut off the oil supply valve for the fire. These actions can be assumed from the state of locomotive cab controls observed following the incident. However, these actions could not stop the train running onto the bridge, which collapsed, pitching the locomotive, tender, and five second class carriages into the river. The leading first-class carriage teetered on the edge of the bridge before its coupling to the rest of the train snapped and it, too, rolled into the river. The remaining three first-class carriages, the guard's van, and a postal van remained on the track.