The Tangiwai train disaster was a deadly railway accident that occurred at 10:21 p.m. on 24 December 1953, when a railway bridge over the Whangaehu River collapsed beneath an express passenger train at Tangiwai, North Island, New Zealand. The locomotive and the 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 rapid mudflow (lahar) in the Whangaehu River, which destroyed one of the bridge piers at Tangiwai only minutes before the train reached the bridge. The volcano itself was not erupting at the time. The disaster remains New Zealand's worst rail accident.
The wreckage of the KA locomotive, the sixth carriage and the rail bridge, in the Whangaehu River at Tangiwai, 25 December 1953.
The destroyed bridge after the disaster
Front page of the Auckland Star newspaper of 26 December
Prince Philip, Duke of Edinburgh, Karori Cemetery, 31 December 1953
The Whangaehu River is a large river in central North Island of New Zealand. Its headwaters are the crater lake of Mount Ruapehu on the central plateau, and it flows into the Tasman Sea eight kilometres southeast of Whanganui. Due to the high acidity of the water coming from the crater lake, water is not diverted from the headwaters for the Tongariro Power Scheme. Instead, it bypasses the Waihianoa Aqueduct via a ford.
The State Highway 49 bridge at Tangiwai