Feasibility of discontinuous electrification on the Great Western Main Line determined by train simulation

The UK has a number of main line railway routes that are not yet electrified. Some of these routes are under active consideration for electrification and the UK Government has recently announced the electrification of the Great Western Main Line (GWML). Railway electrification requires a large capital investment in infrastructure. Areas with limited clearance, such as tunnels and sections through overbridges, are particularly expensive to electrify. In this paper, train performance on the GWML, from London Paddington to Cardiff and vice versa, is modelled for three cases: no electrification; full electrification; and electrification that does not include tunnels, most notably the Severn Tunnel. The modelled trains were: the High Speed Train hauled by pairs of Class 43 diesel-electric locomotives; the nine-car Class 390; and Intercity Express Programme (IEP) trains formed as straight electric or bi-mode multiple units. Bi-mode trains combine electric and diesel traction in the same train. The considered IEP trains included both five-car and eight-car bi-mode options. Journey time, energy consumption and CO₂ emissions were determined in each case. Electrification of the route will result in a reduction in energy consumption, carbon emissions and journey time, with the longest trains offering the greatest benefit. Under normal conditions, all modelled trains were able to complete the journey under discontinuous electrification. However, a small reduction in entry speed into the Severn Tunnel resulted in stalling of the exclusively electric trains. Bi-mode rail vehicles completed the journey in all cases and, as to be expected, also when tunnel entry speed is reduced; journey time, energy consumption and carbon emissions are not majorly impacted compared to exclusively electric operation.