The Expansion is a large project currently underway. Some of the smaller features within the large project include:
- Reconstruction of the Extension Bridge
- Reconstruction of the Tidmouth Lift Bridge
- A small shed
- Several Stations
- A Large Warehouse
- Workmen's residences
- Spotlight Tower
The Little Western Extension was built on the track-bed of a disused line. The Fat Controller had ordered the construction of a new Lift Bridge at Tidmouth to shuttle supplies from the mainland there as quickly as possible. The line of course, had to be refurbished, so Donald and Doc the Ballast Spreader were sent to repair the old rails, apply fresh ballast, and help spray weed-killer on the tracks. Stepney accidentally plunged into the ravine before the Extension Bridge was built.
As winter set in on the project, The Fat Controller borrowed Wilbert from the Dean Forest Railway to assist Arthur with the increased work load. The two manage to keep operations running normally, until Arthur became trapped in an avalanche near the site of his own accidental making.
As the bridge began to connect the two cliff-faces, Duck, Oliver, Donald, and Douglas would often leave their branch to help keep the line in order. Other engines were often called to help out, such as Scruff the Scruncher, whose light weight proved to be very useful for carrying supplies over the bridge. Although Duck and Oliver are anxious to see the line completed, the Fat Controller has made no official statement on who exactly is running the line. Curiously, the Extension uses the strongest steel rails from the Sodor Ironworks that even hold the weight of Murdoch and Hank.
The project has a history of disaster, such as the incident at the Tidmouth Lift Bridge, Stepney's Unfortunate Entrance, The Scaffolding Incident, and The Tornado Incident that split the completed bridge in two.
Construction continues, and the Fat Controller hopes the bridge, and the new line, will be ready very soon. Spamcan has returned to Sodor to help shuttle materials for the extension project.
The Fat Controller arranged a meeting to discuss the opening of the Extension, only to reveal that the meeting was for an invitation to the Extension, much to the dismay of everyone present.
When Richard Hatt made a suggestion box, Daisy entered a rather sassy suggestion to use the supplies from the Extension to make a branch line, which would become the Harwick Branch Line, where she would later work.
- Season 1: Lift Bridge, Stepney Makes an Entrance, Snow Blind, Scruff's Scaffolding, Sidney
- Season 2: Mavis and the Tornado, Aura of Menace, Henry and Kurt, Swashbuckler
- Season 3: The Suggestion Box (mentioned)