The Arlesdale Railway, also called the "Small Railway", is a 15"-gauge railway running from Arlesburgh along the old route of the Mid Sodor Railway to Arlesdale. At Arlesburgh, connections can be made between it and the Arlesburgh branch. The line is mainly used to transport waste materials from several of the abandoned mines at Arlesdale for use as ballast, but it also attracts popularity due to the novelty of being pulled by a 1/3 scale engine.
From Arlesburgh the line stops at Arlesburgh Bridge Street, Ffarquhar Road, Marthwaite, and Arlesdale Green before turning south to Arlesdale. In Adventures on Rails, the old Mid Sodor Railway was restored and the line was extended to Peel Godred.
The ownership of this railway is shared by the Small Controller and the Owner of the Skarloey Railway.
The Arlesdale Railway appeared in Small Railway Engines, Oliver the Western Engine, Duke the Lost Engine, Jock the New Engine, Wilbert the Forest Engine, and is mentioned in Thomas and his Friends. It also appeared in various annuals, Railway Series related books and was mentioned in the My Thomas Story Library book, Duck. It did not appear in the television series, however, some of the engines were made in a few merchandise lines. The Railway was also present on a Japanese map, featuring both Railway Series and Television series locations.
The Arlesdale Railway have not made any appearance in the magazines. However, the magazine story, The Tiny Engine, features a miniature railway which may be the Arlesdale Railway. There is also another narrow gauge branch line alongside Duck's Branch Line, run by a saddle tank engine named, Sidney.
The Ravenglass and Eskdale Railway is the real counterpart of it.
In Adventures on Rails, the line is run by Rex, Bert, Mike, Jock, and Frank. In Sodor Adventures, Blisters I and II also help run the line.