The Huddersfield line is the main railway line between the English cities of Leeds and Manchester via Huddersfield. It is one of the busiest MetroTrain lines. The route travels south-south west from Leeds through Dewsbury. After a short westward stretch through Mirfield (where it runs on the ex-L&YR section), it continues south west through Huddersfield, using the Colne Valley to its headwaters. The long Standedge Tunnel just after Marsden crosses under the watershed and the majority of the run down to Manchester is in the Tame valley. From Manchester, some services continue to Manchester Airport and others to Liverpool.