Human error caused bridge to slip—and trap 1,000 rail commuters, says report
PUBLISHED: 19:48 18 August 2008 | UPDATED: 13:32 05 October 2010
HUMAN error was responsible for a 1,300-tonne bridge dropping several inches while being eased into place over the Liverpool St main line—trapping 1,000 passengers on the tracks below, findings of an investigation revealed this week. Commuters from three packed rush-hour trains had to be rescued by when a concrete block crashed 40ft onto the track from the overhead bridge on May 28
HUMAN error was responsible for a 1,300-tonne bridge dropping several inches while being eased into place over the Liverpool Street main line—trapping nearly 1,000 passengers on the tracks below, findings of an investigation revealed this week.
Commuters from three packed rush-hour trains had to be rescued by police and emergency fire crews when a concrete block crashed 40ft onto the track from the overhead bridge during the evening’s home-going rush-hour on May 28.
Tens of thousands more were delayed when the electric current had to be cut and the network closed for 14 hours.
A support plate slipped just eight inches (200mm) between temporary supports and the base of the bridge being lowered into place to carry the East London Line extension from Whitechapel over the Liverpool Street Line to Shoreditch and Dalston, the report released on Friday found.
The contractors’ working methods were not cleared, either with the site principal contractor Balfour Beatty or Transport for London project engineers, it said.
The 250ft-long bridge slipped after sub-contractors made final adjustments using temporary supports before placing the bridge on its permanent fixtures, the report found.
A change in temperature’ as the bridge cooled is believed to have resulted in the structure contracting by a 10th-of-an-inch (3mm), enough to cause the temporary supports to be ejected’ and five pieces of concrete decking falling onto the busy Liverpool Street main line tracks below.
Transport for London’s rail safety director Martin Brown said: “The work involving jacking the bridge horizontally over the permanent fitting was undertaken without engineers from TfL or our main contractor being aware of what was happening.
“The positioning of the Teflon pad was a human error.
“But the procedures we have should have stopped this error occurring.”
Mr Brown admitted: “No method was prepared for checking—it should have been.
“There is a collective responsibility for ourselves and our contractors to ensure these procedures work.”
The bridge had been inched into place above the main line using hydraulic ramps as trains to Southend, Stansted Airport, Cambridge and Norwich were passing below.
Nearby residents heard a loud thud. One reported seeing the bridge “no longer sitting level.”
The bridge has since been bolted and welded safely into its permanent position. Two other new bridges on the East London Line extension have been checked and given the all clear,’ over Shoreditch High-street and over the Regent’s Canal at Haggerston.
The May 28 incident has not delayed the extension, due to be completed in June, 2010, City Hall assured this week.