The Highland Main Line is a railway line in Scotland. It is long and runs through the Scottish Highlands linking a series of small towns and villages with Perth at one end and Inverness at the other. Today, services between Inverness and Edinburgh, Glasgow and London use the line. At Inverness the line connects with the Far North Line, the Aberdeen-Inverness Line and services on the Kyle of Lochalsh Line. All trains are diesel-powered. Much of the Highland Main Line is single track, and trains coming in opposite directions are often timed to arrive at stations at the same time, where crossing loops permit them to pass. Journey times between Inverness and Edinburgh or Glasgow are approximately three and a half hours. History The vast majority of the line was built and operated by the Highland Railway with a small section of the line between Perth and Stanley built by the Scottish Midland Junction Railway, amalgamated with the Aberdeen Railway to become the Scottish North Eastern Railway in 1856, and then absorbed by the Caledonian Railway in 1866. Originally, the line between Inverness and Perth went via Forres, but the Inverness and Aviemore Direct Railway was opened in 1898 to allow for a more direct routeing. There are two significant summits on the line; Drumochter Summit (also spelled Druimuachdar) (elevation ) between Blair Atholl and Dalwhinnie, and Slochd Summit (elevation ) between Carrbridge and Inverness. Other distinct features on the route include the viaducts at Culloden and Tomatin, the spectacular mountain pass at Drumochter and the severe gradients encountered in both directions, particularly the extended climb from Inverness to the Slochd summit which averages around 1 in 60 the whole way. Initially the only double track was between Inverness and Daviot and also Stanley Junction and Perth. In the 1890s the single line working was improved with the replacement of telegraphing orders to trains along the line with staff and tablet control instruments. This was later upgraded to automatic token-exchange apparatus. However, the main improvement came with the doubling of sections of line, designed by the engineer Alexander Newlands, beginning with Blair Atholl to Dalnacardoch () in 1900, extended to Druimuachdar () in 1901 and Dalwhinnie () in 1909. In the 1960s, many sections of the line were converted from double track to single track. In 1976, 23 miles from Blair Athol to Dalwhinie was redoubled. In March 2019 Network