British Rail Class 710

Class 710 is a development of Bombardier's Aventra electric multiple unit design that is due to be built for London Overground. The contract to provide 45 four-car 75 mph trains was awarded to Bombardier Transportation in July 2015 and the trains are due to enter service in 2018.

Background and specifications
In 2012, TfL announced its intention to procure a fleet of new, longer DMUs, as the units then in service were unable to handle the passenger demand, causing overcrowding throughout the day. TfL issued a tender for manufacturers to supply eight three- or four-car trains. However, this proposal was subsequently shelved when the Government announced that the Gospel Oak to Barking line ('GOBLIN') would be electrified, with proposals instead to purchase a fleet of new EMUs.

TfL invited expressions of interest for a total of 39 four-car EMUs in April 2014, with 30 required for the Cheshunt and Chingford routes, 8 for the Gospel Oak to Barking, and 1 for the Romford to Upminster. Since then the planned procurement has been increased to 45 four-car EMUs, with the additional 6 units intended for the Watford DC Line. The intention is that the five-car trains currently used on the Watford route will be cascaded back to the North London and East London Lines to allow for strengthened services. TfL issued an Invitation to Tender (ITT) in early 2015, and in June 2015 announced that Bombardier had been awarded the contract to build the new trains.

In July 2015 TfL announced that it had placed a £260m order for 45 4-car Bombardier Aventra EMUs, with an option for 24 more, similar to the Class 345s that will be used by Crossrail, for use on the West Anglia Routes and the Watford DC, GOBLIN and Romford to Upminster lines, from 2018, to be known as Class 710. The units will be delivered in two sub-classes; an AC only version with longitudinal and transverse seating (very similar to the S8 units on the Metropolitan line of the London Underground) for use on the West Anglia and Romford-Upminster services, and a dual-voltage version with longitudinal seating for the Watford DC and GOBLIN services. The AC only version will be maintained at Ilford TMD and the dual-voltage units at Willesden TMD.

Fleet details
A total of 45 units totalling 180 carriages are to be built.