The West Coast Main Line is the principal main line linking London to the West Midlands, the North West and Scotland. The majority of rail freight on the line is container traffic. Some of this traffic is marine containers from the southern ports of Southampton, Felixstowe and the recently opened London Gateway to the North West and Scotland. In addition there are domestic containers from Daventry to Scotland. The route also sees other traffic on various sections including cars, cement, china clay, coal, limestone, nuclear flasks, oil, steel and timber, as well as Royal Mail trains linking London, Warrington and Glasgow. On the route there are freight yards at Wembley, Crewe, Warrington, Carlisle and Mossend. The route includes the well-known climbs up to Shap Summit in Cumbria and Beattock Summit in the Southern Uplands of Scotland. On this electrified route freight is hauled by a mixture of diesel and electric locomotives from all the main rail freight operators in Britain. Electric locomotives include Class 86s from the 1960s as well as more modern Class 90s and 92s, through to the recently built Class 88s. Diesels locomotives are mainly Class 66s although some older British Rail-era diesels still operate on certain workings.