Class 378 Capitalstar

The Class 378 Capitalstar was the centre piece of the modernisation of Transport for London's commuter rail network, which was reorganised as London Overground. The Class 378 is part of Bombardier's highly successful Electrostar family. However, there were a number of differences which were specified for London Overground use [1] including "tube style" longitudinal seating, wide gangways and London Underground tripcocks for train protection. Originally they were built as 3-car sets but were soon augmented with a 4th car. Later on increasing demand saw them further strengthened to 5-car sets.
378 206 departs North Wembley

Information
Number built: 285 (57 5-car sets)
Built: 2009-15
Builder: Bombardier
Engine: 3 Bombardier traction motors per motor car (750c DC third rail or 25kV AC OLHE)
Power: 3, 200 hp (2, 400 kW)
Formation: 378/1: Driving Motor Open Standard (DMSO)+Motor Open
Standard (MOS)+Trailer Open Standard (TSO)+MOS+DMSO
378/2: DMSO+MOS+Pantograph Trailer Standard Open (PTSO)
+MOS+DMSO

The Class 378s operate on most lines in the London Overground network with the 378/1s only able to operate on 750v DC third rail equipped lines and the 378/2s being dual voltage able to use 25kv AC overhead line electric collection as well [2]. Strengthening of the fleet to 5-car sets was completed [3] but overcrowding continued to be a problem on the Overground. The arrival of the Class 710 to augment the London Overground fleet has allowed for the 378 fleet to be more heavily concentrated on a a set of routes.
378 214 at Kenton

378 143 at New Cross

Seating aboard a 378

378 216 at Shadwell

378 232 at Blackhorse Road

[1] John Glover, London's Overground (Ian Allan, 2012) p. 106
[2] Colin J. Marsden, DMU and EMU Recognition Guide (Ian Allan, 2013) p. 290
[3] Underground News No. 654 (June 2016) p. 348