Ufa train disaster

The Ufa train disaster was a railway accident that occurred on 4 June 1989, in Iglinsky District, Bashkir ASSR, Soviet Union, when an explosion killed 575 people and injured 800 more. It is the deadliest rail disaster in peacetime in the Soviet Union/Russia.
History.
At 1:15 am, two passenger trains of the Kuybyshev Railway carrying approximately 1,300 vacationers to and from Novosibirsk and a resort in Adler on the Black Sea exploded, from the town of Asha, Chelyabinsk Oblast. Without anyone knowing, a faulty gas pipeline from the line had leaked natural gas liquids (mainly propane and butane), and weather conditions allowed the gas to accumulate across the lowlands, creating a flammable cloud along part of the Kuybyshev Railway. The explosion occurred after wheel sparks from the two passenger trains heading in opposite directions ignited this flammable cloud. Estimates of the size of the explosion have ranged from 250–300 tons TNT equivalent to up to 10 kilotons TNT equivalent. Many of the victims died later in hospital; official figures are 575 dead and over 800 injured, but an unofficial estimate of the number of deaths is approximately 780. 181 of the dead were children; many survivors received severe burns and brain injuries.
On the afternoon of 4 June, Mikhail Gorbachev, Chairman of the Supreme Soviet of the USSR, and members of the government commission to investigate the accident visited the site. The Chairman of the Commission for Investigation of the accident was Deputy Chairman of the Council of Ministers of the USSR Gennady Vedernikov. The trial over the accident continued for six years, nine officials being charged, mostly members of Nefteprovodmontazh (the trust that constructed the faulty pipeline) including the chief of the construction and installation department of Nefteprovodmontazh and foremen. The charges were brought under Article 215, part II of the Criminal Code of the RSFSR, where the maximum penalty was five years imprisonment.
The accident was named after Ufa, the largest city in the Bashkir ASSR, although it occurred about east of the city. An annual commemoration is usually held at the , near the disaster site; there is a memorial at the site.
Factors.
According to Dmitry Chernov and Didier Sornette, the following factors contributed to the disaster:
Another factor, aside from gas leak's factor set, is reported to be negligent of multiple reports about severe presence of gas in the air prior to the explosion.