As part of its 15-year franchise to operate train services in the Wales and Borders area, KeolisAmey undertook the development of the South Wales Metro – an integrated public transport network for the Cardiff and valleys area. Central to this project was the building of a depot at Taff’s Well to house and maintain a new fleet of light rail vehicles (LRVs).
Amey's Transport Infrastructure business, the principal contractor responsible for construction, brought Amey Consulting on board to produce detailed designs for key elements of the facility, including track, telecoms, electrical power, overhead line equipment (OLE) and – crucially – signalling. The depot would not only require its own signalling control system, it would also accommodate a control centre for the signalling on the Core Valleys Line (CVL) (part of the South Wales Metro network).
A fleet of 36 three-car tram-train sets, built by Stadler, were due to be housed at Taff’s Well. Trains would move into and out of the depot via two mainline connections to the north and one to the south. Within the depot trains would pass through facilities ranging from overnight stabling to a maintenance shed, a ‘wash road’ for cleaning, a wheel lathe facility and an area for underframe cleaning.
Unlike most train depots only requiring ‘light touch’ signalling, the complex Taff’s Well depot demanded something more sophisticated. Amey designed a depot control system (DCS) embracing train detection, point machine control, shunt signals and indicators to authorise tram-train movements, an interface to the mainline signalling system, and all associated cabling. The system would be overseen by a depot operations controller from a workstation in the new CVL Integrated Control Centre (ICC).
To maximise safety and flexibility, the designers decided against traditional approved signalling equipment, opting for an innovative approach based on SIL 4 safety PLC (programmable logic control) interlocking technology that evaluates signalling logic and controls trackside assets, and a conventional- COTS based VDU control system. Although developed by Amey Consulting, the system is COTS (commercial off the shelf) based, meaning there is no vendor lock-in. It can be accessed, modified and upgraded by other contractors, with obvious benefits for the rail operator.
The Amey team faced significant challenges. Signalling had been added to the scope of works comparatively late, which meant the signalling infrastructure had to fit into existing track and civil engineering designs. Other issues included uncertainty over the client’s operational requirements and the difficulties of working within a restricted space. At times it was literally back to the drawing board to re-explore different options and adjust aspects of the depot layout.
That an AIP (approved in principle) design was produced in a timely manner is a tribute to the design management process put in place by Amey Consulting. The development of a project integrated model (PIM) and the sharing of technical information was critical to the successful integration of the signalling design within the overall design scheme.