The ruling gradient of the section from Craigendoran to Fort William is 1 in 50, but the line to Mallaig has a ruling gradient of 1 in 40. Seventeen sea wall sections were required between Corpach and Kinlocheil, as Loch Linnhe can be very rough in bad weather. There are eleven tunnels on this section, although originally only two were planned; the longest tunnel is 350 yards long, at Borrodale. There is a swing bridge at Banavie over the Caledonian Canal, and at Glenfinnan the concrete viaduct is 416 yards long on a 12-chain curve; there are 21 arch spans.