British Rail Class 710

Bombardier Transportation
Industry	Rail vehicle manufacturing
Products	Aventra electric multiple units

The British Rail Class 710 Aventra represents a series of electric multiple unit passenger trains manufactured by Bombardier Transportation specifically for the London Overground system. As part of Bombardier's Aventra range, a contract was secured in July 2015 for 45 trains, each consisting of four cars. Although the initial plan targeted a May 2018 launch, the entry into service was postponed until May 2019.

Origins and technical details

In 2012, Transport for London (TfL) intended to acquire longer diesel multiple units (DMUs) to mitigate overcrowding on existing rolling stock. The original proposal involved procuring eight trains with three or four cars each. However, following the Government's June 2013 announcement to electrify the Gospel Oak to Barking line, plans shifted towards electric multiple units (EMUs).

By April 2014, TfL sought expressions of interest for 39 four-car EMUs: 30 designated for the Lea Valley Lines, eight allocated to the Gospel Oak to Barking line, and one for the Romford–Upminster route. This procurement aimed to replace older Class 315 and Class 317 trains dating back to the 1980s, alongside Class 172 units introduced in 2010. Subsequently, the order expanded to include 45 four-car EMUs with an additional six units assigned to the Watford DC line. This strategy permitted redeployment of five-car units from the Watford DC line to the North London and East London Lines, enhancing service capacity. An Invitation to Tender was issued by TfL in early 2015.

Contract award and manufacturing

In July 2015, TfL placed a £260 million contract for 45 four-car Bombardier Aventra EMUs, with options for an extra 24 trains and potential conversion to five-car sets. These vehicles share design similarities with Class 345 and Class 720 models operating on the Elizabeth line and Greater Anglia routes.

The fleet is divided into two subclasses: subclass /1, equipped solely for AC power, serving the Lea Valley lines and Romford–Upminster services; and subclass /2, featuring dual-voltage capability for operations on the Watford DC and Gospel Oak to Barking lines. Subclass /2 units are fitted with pantographs on their PMS(W) cars and undergo maintenance at Willesden TMD, whereas subclass /1 units are serviced at Ilford EMU Depot. Both subclasses feature exclusively longitudinal seating after plans for some transverse seats were abandoned.

In 2017, TfL proposed acquiring nine extra Class 710 trains to boost capacity, utilizing 42 of the additional 249 vehicles available under option. Of these, three would be four-car sets (one designated for the Watford DC line and two for the Gospel Oak–Barking Riverside extension), while six would be five-car sets allocated to the North London and West London lines. This acquisition facilitated redeployment of Class 378 units from those lines onto the East London line. After delivery, the six five-car sets were reclassified from subclass /2 to /3.

Service introduction delays

Testing difficulties caused a three-month postponement in April 2018. By June that year, planned entry into service was deferred until November—nearly eighteen months behind schedule. TfL aimed for deployment in December 2018 but encountered further setbacks.

In January 2019, TfL temporarily operated three Class 378 trains on the Gospel Oak to Barking route while addressing issues with the Class 710 fleet due to expiring leases on existing Class 172 stock. By April 2019, the Office of Rail and Road authorized limited operation of Class 710 units subject to certain operational constraints.

Operations

In May 2019, Transport for London granted approval for the Class 710 trains to enter passenger service. The first pair of these units began running on the Gospel Oak to Barking line starting 23 May 2019, with the entire set of eight units fully operational by August that year. The initial unit commenced service on the Watford DC line on 9 September 2019.

The Class 710 fleet was introduced on the Lea Valley lines on 3 March 2020, following an earlier attempt on 24 February 2020. Operations on the Romford–Upminster route began on 5 October 2020. Specifically, the five-car Class 710/3 units are deployed on the Watford DC line.

Incidents

On 12 October 2021, an eight-car Class 710 train (unit number 710124) overran the buffers at Enfield Town railway station, causing injuries to both the driver and a passenger. Subsequent drug testing revealed the presence of cocaine in the driver’s system, resulting in his arrest for being unfit for duty due to drug use. He was subsequently found guilty of compromising railway safety and received a sixteen-week prison sentence.

Fleet details

Subclass	Operator	Qty.	Year built	Cars per unit	Unit nos.	Description
710/1	London Overground	30	2017–2020	4	710101–710130	AC-only trains operating on the Lea Valley lines and Romford–Upminster line.
710/2		18		4	710256–710273	Dual-voltage trains serving the Gospel Oak to Barking line and Watford DC line.
710/3		6		5	710374–710379	Dual-voltage sets assigned to the Watford DC line and North London Line.