Class 378

Class 378
Name	Class 378
Service	2009–present
Manufacturer	Bombardier Transportation
Family	Electrostar
Yearconstruction	2008–2011
Numberbuilt	54 (3-car units)
Formation	3 cars per unit
Operator	London Overground
Depot	New Cross Gate depot
Lines	North London line, East London line, Gospel Oak to Barking line
Carbody	Aluminium
Maxspeed	75 mph (121 km/h)
Traction	AC traction motors
Collectionmethod	Third rail and pantograph

Class 378 is a British electric multiple unit introduced in 2009 for suburban and urban services in London. Built by Bombardier Transportation as part of the Electrostar family, the units were ordered by Transport for London for operation on London Overground routes and have replaced older units on the North London line, East London line, and other orbital services. The design emphasizes high-capacity, longitudinal seating and wide gangways to increase standing space and facilitate passenger flow on dense urban routes.

Design and Development

Bombardier developed the Class 378 based on the successful Electrostar platform used by National Express East Anglia, Southern and Thameslink operators. The procurement was overseen by Transport for London in response to the Greater London Authority’s goal to expand orbital rail capacity and integrate services with the London Underground and Docklands Light Railway. The design brief prioritized rapid acceleration for short station spacings seen on the North London line, high passenger throughput similar to New York City Subway concepts, and compatibility with both third rail used by Southern and overhead lines employed on extensions serving Crystal Palace and Highbury & Islington. The units reflect contemporary regulatory standards set by the Rail Safety and Standards Board and were delivered to fit depots at New Cross Gate depot.

Technical Specifications

Each 3-car unit is formed of aluminium car bodies with aluminium and steel underframes, powered by AC traction motors controlled by Bombardier’s IGBT-based inverters similar to those in Class 375 and Class 377 fleets. The dual-voltage capability includes a third-rail shoe and pantograph for 25 kV AC overhead, enabling operation across both electrification systems implemented on routes like the East London line and sections connecting to Gospel Oak to Barking line. Bogies derive from designs used under Electrostar variants, employing disc brakes and regenerative braking back to the supply network, compliant with Network Rail standards. Interiors use longitudinal seating to maximize standing capacity and feature wide gangways, CCTV supplied by contractors under contract with Transport for London, passenger information systems compatible with TfL’s standards, and accessibility features to meet the Equality Act 2010 requirements.

Service History

The first units entered passenger service in May 2009 on the North London line following testing overseen by Network Rail and approvals involving the Office of Rail and Road. Early operation coincided with the transfer of suburban lines into the London Overground network under a concession awarded to Arriva UK Trains initially and later operated by Transport for London arrangements. Fleet expansion followed route extensions such as the reopening of the East London line to passenger traffic connecting to stations like Dalston Junction and Clapham Junction. The Class 378s have progressively replaced older rolling stock formerly used by Silverlink and other suburban operators, contributing to capacity increases and timetable recasts promoted by Mayor of London initiatives.

Operations and Deployment

Class 378 units operate intensive, high-frequency services on orbital routes, maintaining short dwell times at busy interchanges such as Highbury & Islington, Shoreditch High Street, and Stratford. Maintenance and stabling are centered at New Cross Gate depot, with periodic works at Stratford depot and coordination with Network Rail possessions for infrastructure upgrades. The units have been deployed on the Gospel Oak to Barking line during electrification phases and on extended services reaching Clapham Junction after the East London line reconnection projects. Operations adhere to timetables negotiated between Transport for London and operating contractors, and crew training incorporated standards from unions such as ASLEF and RMT.

Variants and Modifications

Initial Class 378/0 3-car units were later lengthened to 4-car formations as Class 378/2 through insertion of additional intermediate vehicles, in a process similar to fleet enhancements seen with Class 377/5 and other commuter EMUs. Modifications have included retrofitting additional passenger information displays, upgrading HVAC systems to meet summer performance targets after consultation with London Assembly members, and software updates to traction control units for improved energy efficiency. Some units received modifications for compatibility with platform humps and step-free access improvements driven by schemes supported by Transport for London and local borough councils.

Incidents and Accidents

The Class 378 fleet has been involved in a limited number of operational incidents, typically low-speed collisions and trespass-related delays on densely trafficked urban alignments. Investigations into incidents have been conducted by the Rail Accident Investigation Branch with recommendations for enhanced signage, CCTV coverage, and infrastructure resilience. There have been no high-casualty accidents attributed to design failures; statutory reporting to the Office of Rail and Road has governed remedial action, and subsequent safety measures have been implemented across the London Overground network.

Category:British Rail electric multiple units Category:Bombardier Transportation rolling stock Category:Transport for London rolling stock