Over the Christmas period in 2016, Network Rail carried out extensive resignalling and track remodelling work in and around Cardiff Central station. This was the final stage of the Cardiff area signalling replacement scheme, a project which has been in progress for several years. This stage involved the closure of the power signal box at Cardiff, with control of the area moving to the South Wales Control Centre (SWCC), and changes to the track layout and signalling on the east side of Cardiff Central station.

Some of the new track layout was brought into use on 29 December. At 08:46 hrs on that morning the driver of train 2T08 from Cardiff Central to Treherbert, which had just left platform 7, noticed that a set of points in the route his train was about to take were not set in the correct position. Train 2T08 was the first up train on the Up Llandaff line after the start of service over the new layout.

The points at which the train stopped were redundant in the new layout and should have been secured in the normal position in readiness for their complete removal at a later date. The project works required eight point ends in two separate locations to be locked and secured in this way. In the event only six of the eight point ends were locked and secured, and the line was re-opened to traffic without the omission having been identified by the project team through the normal checking processes which should take place as part of this type of works. These two point ends were left in a condition in which they were unsecured and not detected by the signalling system, and the points at which train 2T08 stopped, points 817A, were left lying reverse. If the driver had not noticed the position of these points and stopped, the train would have been diverted towards line E (the former down relief line) on which trains can run in either direction. The new signalling system uses axle counters for train detection, and in this situation the system would not have identified that the train was in the wrong place.

A few minutes earlier, at 08:24 hrs, another train, down train 1V02, had travelled over the other points which had been left unsecured at the other end of the same crossover (817B). These points had been left in the normal position, which was correct for trains travelling over them in the down direction.

No-one was injured and no damage was caused by either event, and Network Rail acted quickly to secure both sets of points.

Our investigation will examine:

• the events leading up to the commissioning of the new track layout in the area of 817 points
• the methods that Network Rail’s Cardiff area signalling replacement project used for project management and assurance processes
• the on-site team briefing and works management process.

It will also examine any relevant management issues and consider previous relevant recommendations made by the RAIB.

Our investigation is independent of any investigation by the railway industry or by the industry’s regulator, the Office of Rail and Road.

We will publish our findings, including any recommendations to improve safety, at the conclusion of our investigation. This report will be available on our website.

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