The entire railway industry was ordered to improve its safety procedures to prevent a repeat of the derailment at Bexley in south-east London.
The accident happened on 4 February 1997. Seven of the 19 wagons of the ballast-carrying train derailed on a bridge, injuring four people in or near the arches of the viaduct.
The Railway Inspectorate found the accident was caused by the poor condition of the track, the fact that one wagon was overloaded and the excessive speed of the train.
Bob Smallwood, the deputy chief inspector of railways, said yesterday: "The under-lying causes of the accident were failures in management of safety by Railtrack and its contractors."
John Reid, a Transport minister, said he was concerned by the finding of poor management by Railtrack of its contractors. "Railtrack needs to invest in maintenance, put better management structures in place, and must not put profit before safety," he said.
Railtrack and two contractors - South East Infrastructure Maintenance and Southern Track Renewals - were prosecuted for breaches of the 1974 Health and Safety at Work Act. Last September all three pleaded guilty at Kingston Crown Court in south-west London and were fined pounds 150,000.
A Railtrack spokesman said yesterday: "The minute Bexley happened and our investigation was complete we started to implement changes.
"These have been ongoing and were acknowledged by the judge in the case."Reuse content