Waterloo suggests lessons of Clapham crash being forgotten, fears RAIB
The lessons of 1988’s fatal accident at Clapham may be fading from the rail industry’s collective memory, warns the Rail Accident Investigation Branch (RAIB) in its report into August 2017’s derailment of a passenger train at Waterloo.
The train derailed on points that were in neither one position nor the other, after a signal tester added extra wires to interlocking in Waterloo relay room but failed to remove them once testing was complete and the railway reopened. In addition, plans to clamp and lock the points in the correct position were not implemented.
RAIB calls on Network Rail to improve the knowledge and attitudes needed for signal designers, installers and testers to deliver work safely. In addition, it calls on contractors OSL Rail and Mott MacDonald to develop and monitor the non-technical skills of staff working for them.
The accident took place on August 15, during a major blockade at Waterloo that closed Platforms 1-10 while work to lengthen Platforms 1-4 took place. This work meant that the station’s signal interlocking had to be changed. Mott MacDonald designed the changes, and OSL Rail checked them and designed and checked a ‘test desk’ to be installed in Waterloo relay room. This test desk could be connected to the signalling to make it easier to test in advance of physical equipment being installed on the track.
However, RAIB found that poor communication meant that the test desk was not kept up-to-date to reflect changes to the interlocking. This meant that when testers came to check the points on which the train later derailed, the test desk would not work properly without extra wires being added to the interlocking’s electric circuits. When added, these wires fooled the interlocking into thinking all three sets of blades in Points 1524 were in the correct position when only one set actually was (because they were inside the blockade and had been clamped shut).
As a result, signallers could set a route from Platform 11 and clear the signal at the platform end for the 0540 to Guildford. When it left, the train’s driver noticed the points in the wrong position. He braked, but could not prevent his train derailing and striking the side of an engineering train placed to protect the possession from such incursions.
Clapham’s accident in 1988 was caused by signal technicians not properly disconnecting wires, with the result that a signal that should have been red cleared to allow a train past (see pages 48-53).
A subsequent inquiry severely criticised British Rail, and led to radical changes in the way signalling is designed, installed and tested with each stage being done independently of the others.
It is the loss of knowledge of why these changes were made that concerns RAIB. It said in its Waterloo report: “The major changes to signalling design, installation and testing processes triggered by the Clapham accident remain today, but RAIB is concerned that the need for rigorous application is being forgotten as people with personal knowledge of this tragedy retire or move away from front line jobs.
“This deep-seated, tacit knowledge is part of the corporate memory vital to achieve safety. Loss of this type of knowledge as previous generations leave the industry is a risk which must be addressed by organisations committed to achieving high levels of safety,” it said. ■ See Haigh, pages 54-55.