Built: 2010
Manufacturer: Bombardier Transportation, Derby
Entered Service: July 2010
Withdrawn From Service: March 2019
Number in Service:  8
Number of Carriages per Train: 2
Seats per Train: 124
Passenger Capacity: 350 (approx.)

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Train Length: 154ft 11in
Train Width: 8 ft 9ins
Train Height: 12ft 4ins
Train Weight: 83.2 tonnes

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Class 172 Diesel Multiple Unit History

Upon taking control of the former Silverlink Metro services in November 2007, Transport for London inherited a small fleet of Class 150 diesel multiple units to operate services on the Gospel Oak to Barking line.

One of the first realisations of the company was that, due to the mechanical unreliability of the incumbent units, new rolling stock would need to be obtained. As part of the procurement process, TfL approached Bombardier Transportation regarding their ‘Turbostar’ product, already in use with several UK operators.

The unit chosen was a lighter-weight variant of the popular Class 170, featuring longitudinal seating and hydraulic gears. The eight two-car units were purchased by Angel Trains, who leased them to London Overground and they started to enter service in July 2010, with full assumption of service in December of that year.

The overwhelming success of the London Overground services within their first 2 years led to the 2-car units becoming insufficient in capacity terms, with trains regularly filled beyond capacity. London Overground began a process to either add a third carriage to the trains or replace them completely with brand new 3 or 4-car DMUs.

The replacement process was turned on its head in June 2013, when the UK Government announced that the Gospel Oak to Barking line was to be electrified as part of a wider strategy. this led to a £260m order for 45 four-car Bombardier Class 710 Aventra Electric Multiple Units to replace the incumbent units on the Gospel Oak to Barking, Lea Valley Line and Watford DC Lines services.

The Class 172 units were due to begin being cascaded to West Midlands Trains in November 2018, with the introduction of the new Class 710s. However, the transfer did not occur as planned and the Class 172s did not leave the line until March 2019, being temporarily replaced by shortened Class 378 EMUs redeployed from other London Overground Lines.

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