How Britain transformed surplus electric trains into versatile bi-mode regional workhorses
In short: When Britain’s aging Class 319 electric trains became surplus to requirements, engineers saw an opportunity rather than scrap metal. By retrofitting these units with diesel engines, they created the Class 769 Flex, a bi-mode train capable of switching between electric and diesel power while in motion to bridge gaps in the network.
The Class 769 Flex project began as a strategic response to electrification delays and a shortage of diesel multiple units. Porterbrook, the owner of the original Class 319 fleet, partnered with Brush Traction to convert these four-car units. The core of the transformation involved installing two MAN D2876 diesel engines—one under each driving trailer—to power the existing electric traction systems. This engineering feat required over 45,000 hours of design work and the creation of more than 2,500 technical drawings to integrate the new powerpacks, exhaust systems, and fire suppression measures into the existing architecture.
A primary challenge was maintaining the train's balance and performance. The conversion added approximately 7.5 tonnes to each driving trailer, necessitating adjustments to the original suspension and braking systems. To ensure the trains remained attractive to operators, engineers aimed for performance levels equal to or better than the Class 150 Sprinter. The resulting design allows drivers to seamlessly switch between overhead AC, third-rail DC, and diesel power sources. This flexibility is particularly valuable on routes that are only partially electrified, enabling continuous service across varied infrastructure without requiring passengers to change trains.
The rollout of the Class 769 has been complex, marked by significant delays and shifting operational plans. While Transport for Wales introduced the units into service in November 2020, they withdrew their entire fleet by May 2023. Northern Trains eventually launched their units in May 2021, and in 2025, they acquired additional sets to support maintenance cycles. Meanwhile, a major plan for Great Western Railway to operate nineteen units was abandoned in December 2022 due to service level cuts. Despite these hurdles, the project continues to evolve, with recent interest in converting units for parcels transport and potential new passenger services, demonstrating the ongoing search for utility in repurposed rolling stock.
Opens the Intellect+ feed with this card first. Swipe up for the next one.
Sources
- Summary by Intellect · source: British Rail Class 769
- Also: Wikidata — British Rail Class 769 · CC0
To cite this card, link to https://intellectplus.co.uk/app/places-british-rail-class-769.
How we source, check and correct cards: Editorial standards.
General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.
Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?
Related
More in UK & Irish cities · More in Countries & Cities · Latest · A–Z · All topics
