The British Rail Class 378 Capitalstar is an electric multiple unit passenger train specifically designed for the London Overground network. It is part of Bombardier Transportation's Electrostar family. A total of 57 five-car trains have been built – most of which were originally built as three- or four-car units. The Class 378s were ordered in August 2006 in response to passenger dissatisfaction with existing mass-transit trains operated by Silverlink, such as the ageing fleet of Class 313. The procurement of a modern replacement was viewed as yielding better performance than the refurbishment of the existing units. Accordingly, a total of 57 Class 378s were manufactured at Bombardier's Derby site, the first example of which entered revenue service during July 2009. The type's introduction was roughly half a year later than originally planned, largely as a result of difficulties with multiple suppliers. In design terms the train is broadly similar to the Class 376 trains operated by Southeastern, featuring the same wider metro-style sliding pocket doors for more efficient boarding and alighting. However, it also has significant differences from the Class 376, such as fully longitudinal seating similar to that used on London Underground rolling stock to give more standing and less seating capacity and reduce overcrowding, the interior having been optimised for the high-volume metro-style services being operated by London Overground. History By the start of the twenty-first century, several types of rolling stock that had originally entered service multiple decades before were in operation across London. In particular, the Silverlink franchise on the North London line was frequently regarded by travellers as having offered a poor service, complaints centering around extremely congested trains and unreliable service. The Class 313 was being used for these services at this time; its interiors were of noticeably lower quality compared to that of newer trains, and the trains themselves were viewed as unwelcoming to passengers, particularly during late hours. Officials at Transport for London (TfL) were motivated to improve the situation and decided on a modern replacement for the Class 313. Accordingly, they began to investigate various options for doing so. In August 2006 it was announced that a contract worth £223 million had been signed between rolling-stock manufacturer Bombardier and TfL, under which an initial batch of 152 individual cars would be supplied, deliveries of which were to start in September 2008. The original contract contained an option to purchase additional cars,