A CRIMINAL investigation into the cause of the fatal rail crash at Potters Bar last Friday is focussing on why two sets of critical nuts were undone at a set of points causing the train to derail.
An interim report released by the HSE's Railway Inspectorate on Tuesday confirmed that the two pairs of bolts were missing from 'stretcher bars' which are critical to the functioning of the points (see diagram page 6).
Seven people died and 76 were injured when the last carriage of the four-coach 12.45 London Kings Cross to King's Lynn service travelling at 160kph left the tracks at points 150m south of Potters Bar station, eleven minutes into its journey.
The carriage ploughed into the station before wedging under a platform canopy. Massive destruction included severe damage to a rail over bridge just south of the station (see box page 6). One woman was killed by flying debris hurled from the bridge onto the road below.
British Transport Police and Health & Safety Executive railway inspectors are due to interview senior Railtrack managers and staff from its line maintenance contractor Jarvis to find why points 2181A failed despite having being inspected the day before.
Loss of the bolts from the points disengaged two of three stretcher bars, placing excessive load on the front one. This failed when the last bogie of the third carriage passed over. The dead and injured on the train were in the carriage which derailed.
'The bolts secure the points in place but had worked loose. We don't know why, and will be checking both the maintenance records and fabrication details as part of our forensic investigations, ' said Her Majesty's Railway Inspectorate (HMRI) head of operations Dr Bob Smallwood.
Inspectors at the scene said that they believed the mechanism of failure to be unprecedented and that it was unlikely that the bolts had fallen off due to vibration.
The HMRI inspector leading the Potters Bar investigation said that loose bolts were reported at the same points during an inspection on 1 May. 'A record from Jarvis maintenance people in the Potters Bar area confirms that nuts at the points were loose, ' said Frank Hyland.
A visual inspection on 9 May, the day before the accident, did not report any fault with the points. Jarvis maintains that the nuts were re-tightened once found loose on 1 May.
Hyland said that after the accident, four detached nuts were found underneath the stretcher bars, two at the end of each. The points have been removed to HSE laboratories in Sheffield for detailed forensic investigations. He said that details of whether the nuts were new or old, the condition of the bar threads or the nuts themselves would be determined by the forensic investigation. This will also examine if vibration could have caused the nuts to work loose.
The possibility that the bolts could have been removed by vandalism seemed remote as NCE went to press. Dr Smallwood said removal would require specialist large spanners as well as access to the railway.
'Vandalism would have to be extremely sophisticated and daring, ' he said.
HMRI head Dr Allan Sefton said that no initial findings were available because of the detailed nature of the inquiry. 'It is not a case of people trying out nuts on bolts on site to see if they work - all this work needs to be carried out in laboratory conditions, ' said Dr Sefton.
Railtrack chief executive John Armitt, ordered checks to be carried out on all similar points immediately after the disaster. Key junctions as well as a representative sample around the country were chosen initially, with further tests to continue until all 2,000 similar sets are examined.
By Tuesday, over 800 points had been checked, with the remainder expected to be examined within three weeks.
Smallwood said although work was required at a number of locations, a repeat of the same fault had not been found. 'No defects of the extent and character of the Potters Bar fault have been replicated elsewhere, ' he said.
Armitt said that since joining Railtrack at the start of the year, he was satisfied that rail safety was Railtrack's top priority.
Jarvis took over responsibility for the East Coast Main Line maintenance from Balfour Beatty after winning the £250M contract in April 2001. This followed the October 2000 Hatfield Rail disaster. Hatfield is only 10km from Potters Bar.
Despite Friday's horror, a disaster of even greater unthinkable proportions was avoided only by chance, as express GNER 225 services passed over the same points shortly before they failed.
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Causes slip through reporting net
THE RAILWAY industry's Confidential Incident Reporting and Analysis System (CIRAS) is not designed to deal with the sort of incident that may have caused the Potters Bar crash last week, a spokeswoman said on Tuesday.
CIRAS was set up in June 2000 after the Ladbroke Grove train crash.
'If someone reports an urgent safety problem we can only encourage them to pursue it through normal channels, ' she said.
'Our job is to collate reports on incidents that probably would never get reported any other way, identify any trends or patterns and deal with them via the CIRAS representatives within the member companies.'
'We are not a regulatory body or a whistleblower, we're an incident logging, data collecting organisation which is complementary to normal reporting channels, ' she said.
Reports from railway personnel concerned about safety are usually edited to protect the identity of the person involved then passed on to the relevant organisation, but this could take up to a month, according to the spokeswoman.
CIRAS, like the similar CHIRP body which operates in the airline industry, is more interested in the human factors that can cause train crashes, rather than purely technical issues.
Staff turnover strips inspection expertise
HIGH STAFF turnover in the rail industry has created an inexperienced track inspection workforce, a Rail, Maritime & Transport workers union spokesman said this week.
In the past, the industry was staffed by time-served workers.
Now, experienced workers are a minority in permanent way gangs, he claimed.
A senior industry source said across the board skills shortages compound the problem. There is a particular dearth of testing engineers, he said. Railtrack is to trail blaze a new consolidated and cohesive training policy to counter the engineer drought.
Railtrack has sought to increase its own engineering staff since last year (NCE 24 January) and now has around 1,000 engineers. This is some 100 more than it had last year and the track operator aims to see a similar increase over the next year.
Workers, including subcontractors and agency workers, must hold a personal safety certificate to work on the tracks, awarded on passing a two day course which must be renewed every two years.
The course covers instructions, safety regimes, general site safety, and communication procedures.
Further qualifications are needed before workers can carry out safety critical track inspections.