The Class 378 Capitalstar is a type of electric multiple unit train, part of Bombardier Transportation’s Electrostar family. These trains are operating on the London Overground network, for which they were specifically designed. The design is derived from the Class 376 trains used by Southeastern, featuring the same wider metro-style sliding pocket doors for more efficient boarding and alighting, which are faster and more reliable than plug doors, although they do not close flush with the bodyside and hence are less aerodynamic and do not provide as much heat insulation. However, they also have significant differences from the Class 376, such as fully longitudinal seating similar to that used on London Underground rolling stock to give more standing room, suitable for the high-volume metro-style services on London Overground. The units also have end gangways, though these are intended for emergency use only. The units were initially announced as coming in two separate batches.