Main Line (Thomas and Friends)

The North Western Railway Main Line travels from Barrow westward to Tidmouth through southern Sodor. It is approximately 80 miles long.

Operations and stations
The main line starts from the English town of Barrow-in-Furness. Crossing over the rolling lift bridge across the Walney Channel, the line calls at Vicarstown before passing through Henry's Tunnel. After this, the junction to the Norramby Branch Line is reached.

After Vicarstown, the line calls at Crovan's Gate, home to the Works and the Skarloey Railway. After stopping here, the line travels to Kellsthorpe Road, junction to The Kirk Ronan Branch Line. The line afterwards reaches Killdane, junction to the Peel Godred Branch Line.

Cronk is next, and once leaving the station, trains cross a viaduct, and then arrives at Maron, junction to the Ulfstead Branch Line. Trains then descend Gordon's Hill and pull in at Wellsworth, the junction to Edward's Branch Line. Trains arrive at Crosby, pass through a mile-long tunnel, and then stop at Knapford, the junction to Thomas' Branch Line. The main line terminates at Tidmouth, home to the headquarters of the North Western Railway and the main line sheds. The junction to Duck's Branch Line is here as well. The main line carries several kinds of freight, including ballast, lead, zinc, silver, slate, bauxite, produce, building stones and fish, including the Tidmouth kipper, which is considered a delicacy. Tourism is a major part of the passenger traffic during the summer season, as Sodor has many beautiful lakes, mountains, and other beautiful scenery. The main passenger traffic is commutering, with either stopping trains that stop at all main line stations or the "Wild Nor' Wester", the railway's express, which stops only at the Works station before reaching the Other Railway.

Main Line loop
In the television series, there is a loop of the line between Maron and the Whispering Woods.

The line starts at Maron and then calls at Sodor Airport, the Sodor Search and Rescue Centre, Killaban and Cabalnoo before returning to the main line at the Whispering Woods. A repair yard, Jem Cole's Yard, Sodor Grain Windmill, an abandoned mine and the Sodor Maritime Museum are also located along this line.

Engines
The line is staffed by Gordon, who usually pulls fast passenger trains, Henry and James, two mixed-traffic engines, and Bear, who assists with passenger duties. Donald and Douglas and the Works Diesel help out with shunting duties and goods trains. Pip and Emma take the "Wild Nor' Wester" from Sodor to London.

In the television series Emily and Murdoch also work on the line.