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The 'Welham Green curve'

The scene of the Hatfield train crash
The scene of the Hatfield train crash
Image from The Health and Safety Laboratory
On 17 October 2000, an InterCity 225 train bound for Leeds left London King’s Cross at midday heading north on the East Coast Main Line. It passed through North Mymms travelling at 185 km/h (115 mph) before encountering the 'Welham Green curve' where it started to derail before travelling a further 1km to a point south of Hatfield. Four people died and 70 were injured.

The final report by the Office of Rail Regulation (ORR), July 2006, concluded that the "immediate cause of the derailment ... was the fracture and subsequent fragmentation of the [outer] rail on the [northbound] fast line at the Welham Green curve". The rail failure, according to the board, was due to the presence of "multiple and preexisting fatigue cracks in the rail".

The issue of the "preexisting fatigue cracks" on the Welham Green curve had been known for some time.

The cover of 'East Coast Main Line Disasters'
According to Adrian Gray, author of 'East Coast Main Line Disasters' published in 2013 and available on the Internet Archive, replacing the track on the Welham Green curve had been considered an urgent priority by engineers.

In late 1999, almost a year before the Hatfield crash, an issue with a rail in Durham had "given rise to widespread concern" among Railtrack's engineers about 'gauge corner cracking' (GCC).

Writing in a parliamentary report on GCC before the Hatfield crash, the then rail regulator, Tom Winsor, described what GCC looked like.
"The GCC cracks appear as a series of transverse cracks across the top of a rail (the running surface), and they may extend down the inner vertical face of the rail. In the early stage of development these cracks are fine, hairline fractures, that may not even be immediately visible to the naked eye."
Winsor's report continued by describing the possible consequences of leaving GCC untreated.
"Continued loading under traffic causes these cracks to grow. Crack growth initially occurs at shallow depth (a few millimetres) below the rail surface. However, if left unchecked, two things tend to happen. The near-surface cracking can lead to significant spalling or "shelling", where the rail surface actually begins to break up and pieces of metal come away, leaving the rail surface pitted and corroded."
Railtrack's LNER engineers were so concerned about GCC that a review of the entire East Coast Main Line was carried out. The review, which took place in early 2000, identified a number of "priority sites" where similar problems were "a significant risk".

These sites were each accorded a priority level. The "high speed curves through the Hatfield area at Hatfield itself and at Welham Green just to the south" were identified as "some of the highest priorities".

Repair work was scheduled to start on the Hatfield section then move on to the Welham Green section in May 2000.

However, engineers decided to bring the work at Welham Green forward to April after the state of the rails was considered to be "an urgent matter".

Repair work at Welham Green was then rescheduled for the third week of April. Rail was delivered to the site on April 28.

But those replacement rails were to be left lying alongside the faulty track for six months. Gray wrote that "over-running work at Hatfield caused further delays for rerailing at Welham Green".

In Chapter 4 of his book 'East Coast Main Line Disasters' Gray wrote that "dates were suggested into the start of the next year". He also noted that "problems at the site" (Welham Green) were well known and that "rails laid in 1982 had been replaced in 1995."

The "start of the next year" would have been January 2001, two months after the fatal crash. Gray wrote that the constant delays were motivated in part by worries over delays to trains.
"As the final report stated, Railtrack was biased towards performance-driven decision and train delays was the most significant target. There was a marked reluctance to impose speed limits. At the same time the condition of the track was inspected weekly by staff from Balfour Beatty Rail Maintenance but they, together with engineers from Railtrack, had a difficult job making visual inspections of rails on a high speed main line with curves because of the staff "protection" arrangements."
Gray noted that engineers faced particular problems examining the track at Welham Green due to the speed of approaching trains. As a result they were not always able to conduct close inspections.
"At Welham Green, staff on the track would only have a four-second sighting of an approaching express and so inspection was often conducted from the cess rather than on the track."
The "cess" is the area at the side of the track which is used as a walkway or refuge for staff working on the track.

The official inquiry into the disaster by the HSE (Health and Safety Executive) stated that the maintenance contractor at the time, Balfour Beatty Rail Maintenance Ltd (BBRML), "failed to manage effectively the inspection and maintenance of the rail at the site of the accident". The investigation also found that Railtrack PLC, the infrastructure controller at the time, failed to manage effectively the work of BBRML.

Similar blame was registered by The Royal Academy of Engineering which published a report into the crash:
"A preliminary investigation found that the rail had fragmented as trains passed and that the likely cause was rolling contact fatigue (RCF). Repeated high loading caused fatigue cracks to grow. When they reached a critical size, the rail failed. Portions of the failed track at Hatfield were reassembled and numerous fatigue cracks were identified".
Rolling contact fatigue (RCF) is a group of rail damages which manifest themselves on the surface or close to surface inside the rails due to over-stressing of the rail material.

Almost five years later, when Network Rail (which at the time of the crash was known as Railtrack) appeared in court, Richard Lissack QC, prosecuting, indicated that problems at the Welham Green section of the track were known about months before engineers examined and prioritised repair work:
"A faulty rail at the crash site that had been identified 21 months before the crash but not fixed, even though a replacement had been delivered and left alongside it for six months."
A month later the engineering company Balfour Beatty was fined £10m and Network Rail £3.5m for "breaking safety rules before the crash". The companies were ordered to pay £300,000 each in legal costs.

Gray also noted that following the crash pieces of the rail were taken to Sheffield for analysis. Gray quotes the final engineers report as recording that "the rail fracture was due to the presence of multiple pre-existing failure cracks". Gray expanded on what that report stated:
"In fact there were two sections that disintegrated. The first section of 35m length broke into over 300 pieces and there was then a 44m section that remained intact, followed by a further 54m which also fragmented. The rails on the curve had been subjected to fatigue caused by trains with 'out of round' wheels with flat sections, also by poor jointing and poor packing under the rail."
"In these conditions stresses might develop into fractures or cracks and at Welham Green there was found to have been extensive cracking which became known as 'rolling contact fatigue’."
The crash of 17 October 2000 is not the first close to Welham Green. The North Mymms History Project has details of two more.

Clearing the 1946 Welham Green derailment
Clearing the 1946 Welham Green derailment
Photograph from the Peter Miller Collection
On Sunday 10 November 1946 a London-bound express train derailed about 200 yards south of the Dixons Hill Road bridge, Welham Green. On a section described as “troublesome” by rail workers.

The entire train derailed, apart from the leading wheels of the engine. There were no serious casualties, although seven people complained of minor injuries and shock; none required hospital treatment.

The Redhall signal box north of Marshmoor where the train stopped
The Redhall signal box north of Marshmoor where the train stopped
OS six-inch map 1883 courtesy of the National Library of Scotland
On a frosty Boxing Day evening in 1870 a wheel on a north-bound train travelling through North Mymms fractured sending carriages down the embankment at the Marshmoor railway crossing near Welham Green.

Eight people died that evening, including two local women - sisters-in-law - who were walking close to the line. Three people were injured.

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