The Chancery Lane Tube crash should have been prevented, according to a final report by London Underground (LU).
The train derailed and hit the tunnel wall at Chancery Lane
Dr Roger Aylward, the independent chairman of LU's investigation into the derailment in January 2003, said underlying causes of an earlier incident had not been understood.
The Central Line was suspended for months after a train derailed, injuring 32 people.
But rail unions and campaign groups are now asking questions as to why 39 members of staff received bonuses for their efforts in the aftermath of the derailment.
LU, which has defended giving the £1,000 awards, said they were handed out for "Herculean efforts" after the crash.
Some of the awards have gone to senior managers who were criticised in Friday's final report into the accident.
The Rail Maritime and Transport (RMT) union has asked LU for an explanation as the driver of the derailed train, who was given a gold award for helping passengers to safety, only got £250.
An independent inquiry team found the Tube train crashed after a traction motor beneath the train fell off and hit the track.
The cause of this was gearbox failure which in turn caused the traction motor to become detached.
'Room for improvement'
Dr Aylward said: "The report clearly describes that, following an earlier incident at Hainault (on the Central line), the underlying causes were not understood and this serious incident was not prevented as it should have been."
LU's managing director Paul Godier said: "Despite the Tube's good - and improving - safety record and well-developed safety management system, this report shows mistakes can and still do happen.
"There is room for improvement and we therefore accept all of the recommendations."
Twenty-four recommendations were made in the report so Tube bosses could "address the deficiencies identified".
- The original design of the motor fixings and safety brackets was inadequate, but this had only recently been recognised
- Previous investigations into earlier motor fixing problems were not sufficiently far reaching and failed to uncover this design flaw, or make the connection with related gearbox failures
- As a result, the precaution of checking bolt tightness did not prevent the problem recurring
- Operational measures to deal with any such recurrence were not sufficiently in place
- Gearbox failures are caused by fatigue and the implications of earlier failures were not detected
- The failure of bearings in the gearbox results in very high loading on the motor fixing bolts, which they were not designed to withstand. In turn, the safety brackets were not capable of fully retaining the motor. The bolts and brackets failed and the motor fell to the track, causing the derailment