RENEWAL CONTRACTOR Jarvis failed to replace the broken rail which caused last week's Hatfield train crash because Railtrack was unable to give it enough track possession time to carry out the work.
Jarvis said it needed an eight hour track closure to replace the rail but had been unable to secure a long enough time slot until next month. It had been told to do the work last March.
The crash happened just 14 minutes into the train's journey from Kings Cross to Leeds, killing four passengers. It was travelling through a right hand curve when the back section of the train derailed.
During track replacement possessions, powering down the overhead electrification network would take the initial hour.
The section to be re-railed would then have to be unclipped manually before the old line was lifted clear.
Once the new rail was laid in place it would have to be clipped manually. It would then have to be stressed and the overhead lines re-powered.
The length due to be replaced was approximately 400m of continuously welded rail.
Faster replacement is possible using a track laying machine but these are expensive and not used widely.
Jarvis recently bought a P118s machine capable of laying 400m of track per hour. But it is the only one in the UK and is in use on the West Coast Main Line modernisation programme.
Railtrack had originally instructed Jarvis to replace the rail in March after Balfour Beatty inspected the line in January.
It is believed that in earlier talks between Railtrack and Jarvis, five-hour possessions were discussed but rejected as being too short.
In the end the work was scheduled to take place as part of a series of five eight hour possessions in November and December.
The Hatfield section of track was one of six in the region, with replacement classed as essential.
At the time of the crash the other five sections had been replaced. Railtrack and Jarvis agreed a series of possessions for the replacement of the section a few hundred meters north of the crash scene in May.
The replacement rail for the section where the crash occurred was also delivered to site in May.
Crash investigators are examining the contents of Balfour Beatty's January report which initially highlighted the condition of the rail.
A Balfour Beatty spokesman said the report indicated that renewal was required but that this did not necessarily mean within a specific timespan.
This could explain why speed restrictions were not put in place to safeguard passengers until the re- railing.
The failed rail was only five years old. Although the average life expectancy of rail is 30 years, the line is on a curve which has particularly high traffic volumes travelling at high speeds.
On other parts of the network poor quality steel has been linked to broken rails. This was the case on the West Coast Main Line between Rugby and Watford where a number of broken rails were encountered on relatively new track.