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; 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. In November 2011, the Government announced that this route would be electrified, to be completed by 2022; however, there have been multiple delays. It is currently subject to the Transpennine Route Upgrade, which is an element of the Integrated Rail Plan for the North and Midlands that was announced in November 2021. History At the time of the 1923 Grouping, most of the route followed by the line was over London and North Western Railway (LNWR) metals; the exception was a short stretch around Mirfield, which was the property of the Lancashire and Yorkshire Railway (L&YR). The first section of the line, between Huddersfield and Stalybridge, was opened by the Manchester, Stockport and Leeds Railway on 1 August 1849. The line became part of the London, Midland and Scottish Railway after 1923. The route was furnished with an additional two tracks in 1894, thus giving four tracks between Stalybridge and Leeds. The loss of traffic through the second half of the 20th century saw these cut back to just two lines and the closure of the Micklehurst (Friezland) loop. The length of the line between Manchester Victoria and Holbeck Junction at Leeds is , though the Transpennine upgrade work covers the additional section to York which accounts for . Future From spring 2019, the whole route is being upgraded over the course of three control periods extending beyond 2029. Network Rail state that this will include doubling the track in some places and upgrading stations as well as some of the intended Transpennine north railway upgrade. The electrification was to have been curtailed in parts and, as such, the sections between Stalybridge and Huddersfield, with a further section of east of Leeds, was not to have been electrified. Emphasis was placed on the bi-modal power of the new trains using the line; this necessitated