Trains, entered service in 2010. At first their speed was restricted to but the restriction was lifted when a test was found to be flawed. TfL invited expressions of interest for a total of 39 four-car EMUs in April 2014, with 30 required for the Lea Valley lines, eight for the Gospel Oak to Barking line, and one for the Romford–Upminster line all to replace older Class 172, Class 315 and Class 317 trains. Since then the planned procurement was increased to 45 four-car EMUs, with the additional six units intended for the Watford DC Line. In July 2015, TfL announced that it had placed a £260M order for 45 four-car Bombardier Aventra EMUs, with an option for 24 more, for use on the Lea Valley lines and the Watford DC line, Gospel Oak to Barking line and Romford–Upminster line from 2018. The type will be known as the and will be similar to the used by Crossrail. Nine further units were ordered in February 2018, split between an additional three Class 710/2 units for use on the extended Gospel Oak to Barking line, and six 5-car units to allow Class 378 units to be cascaded to strengthened East London line services. On 22 May 2019, TfL announced that approval had been gained for the Class 710s to enter passenger service. The first two units entered service on the Gospel Oak to Barking line on Thursday 23 May 2019 and the remaining six were in service by August 2019, with the first unit entering service on the Watford DC line on 9 September 2019. The first units on the Lea Valley lines entered service on 3 March 2020 after a first attempt on 24 February 2020. Their use on Romford–Upminster line services began in October 2020. Current fleet Past fleet Former train types operated by London Overground include: Livery All Capitalstar and Aventra stock in service now carries Overground livery. It is similar to Underground livery, and consists of white and black coaches, a longitudinal thick blue stripe and a thin orange stripe along the bottom, London Overground roundels at midpoints along the coaches, black window-surrounds and orange doors. The ends of each Class 378 unit are painted yellow to comply with the National Rail standards that existed when the first wave of new trains began to enter service in 2009. However, Class 710 units do not have this as