and South London line. The transfer of some suburban services from Liverpool Street in May 2015 from the Greater Anglia franchise to London Overground also distorted numbers, contributing to a very large growth between 2014/15 and 2015/16. Rolling stock Since the London Overground took over from Silverlink, TfL has pursued a programme of rolling-stock replacement in order to remove from service the ageing second-generation EMUs and Class 150 DMUs it inherited from Silverlink. In 2009, Class 378 Capitalstars built by Bombardier's Derby Litchurch Lane Works were introduced on the electrified lines to replace the and units used previously, while the Class 150s were replaced by new Class 172 Turbostar units on the non-electrified Gospel Oak to Barking Line. By October 2010, the new rolling stock had completely replaced the units previously operated by Silverlink. The Class 313 and 150s were cascaded to other train operating companies Southern, First Capital Connect and First Great Western. The Class 508 units were stored at Eastleigh Works but were subsequently scrapped in 2013 after being deemed unfit. Before its closure to become part of the London Overground, services on the East London line were operated with London Underground A60 and A62 Stock. The Class 378 trains were officially unveiled at on 13 July 2009. They include a number of tube-style features, including longitudinal seating and increased standing room to provide a high-capacity metro service. They also benefit from walk-through carriage interiors and air conditioning. The North London line has a base fleet of 24 four-car units, Class 378/2. However, these were delivered as three-car units (378/0), with the extended trains being introduced from September 2010, following platform extension works and delivery of the first 20 four-car units (378/1) for the East London line. A further 13 dual-voltage units were delivered to expand services, taking the total fleet to 57 four-car units. These trains are to be extended to five-car sets towards the end of 2014, starting with the East London line sets. The trains are leased from newly formed rolling stock company (ROSCO) QW Rail Leasing until 2027. TfL planned initially to buy the new fleet outright, but in February 2008 announced that it would lease the trains in order to free up the £250 million capital cost of purchase, combined with reducing the risk of making a loss through any future sell-on of the fleet. Eight two-car Class 172/0 units, leased from Angel