The project involves electrifying almost 13 miles of infrastructure and lengthening platforms between Wigan North Western station and Lostock Junction near Bolton.
The £78m upgrade project will provide 450 new overhead line equipment stanchions, and modifications to 17 bridges and two-level crossings.
Platforms will also be extended at Hindley, Westhoughton and Ince stations to reduce overcrowding at peak times and cater for six-carriage trains in the future.
Target completion date is before April 2025.
Network Rail northwest route director Phil James said: “This environmentally and passenger-centric scheme will be a game changer for Greater Manchester’s railway as more electric trains mean better air quality, less railway noise and more reliable and spacious journeys for rail travellers.”
The Department for Transport said that the project would provide train operators with more operational flexibility to deploy trains to these parts of Wigan and Bolton from the recently upgraded train maintenance facility at Wigan Springs Branch.