Streamlining design coordination: connecting High Speed Two to the West Coast Mainline

The High-Speed route joins the West Coast Main Line at Handsacre Junction just North of Lichfield, enabling HS2 Phase One services to continue North to Crewe and beyond.

All High Speed Two design and construction for assets such as civil structures, track and overhead power is undertaken within the same engineering coordinate system, called the HS2 Survey Grid. The West Coast Main Line is an Absolute Track Geometry route, and the asset information including rail alignment is maintained in the West Coast Grid.

The HS2 Survey Grid is well defined and understood, however the West Coast Grid is a legacy grid with no formal definition as defined purely by ground markers. To enable design coordination at the interface between High Speed Two and the West Coast Mainline, a workable transformation between the two systems is required.

This paper presents a new approach for transforming design between the two systems that uses the Transverse Mercator with Affine Postprocess (TMAF) projection, with the major benefit of building upon existing capabilities within design software such that data exchange is streamlined, and transformation risks are minimised with greater compatibility between complex design models and other data sources.

The derivation of the West Coast Grid TMAF, applicable to Handsacre Junction, results from a collaboration between High Speed Two and Network Rail. It is fully documented here including validation featuring ‘in situ’ survey control observations showing transformation accuracy to within ±4 mm.

The implementation of the TMAF process has clear impact on design coordination and advantages include the optimal coordination of the track alignment interface. It is expected to bring similar efficiencies at further points along the High Speed Two route.

The new approach is a significant step forward in coordinating interfaces with assets managed in legacy engineering grids and being fully generic is therefore applicable on other projects beyond rail.