This project involved the procurement of both wholly electric units (Class 801), and "bi-mode" trains (Class 800), powered by electric traction motors capable of running from overhead electric wires or on-board diesel generators. These trains were intended to replace the existing High Speed Trains following the electrification of the Great Western Main Line. However, electrification will only go as far as Cardiff Central, while the route beyond Cardiff continued to require diesel traction (hence the need to procure trains capable of operating without overhead wires).
