The Chiltern Main Line is an intercity regional and commuter main line railway in the United Kingdom, part of the British railway system. It links London and Birmingham on a 106 mile route which runs via North West London, Buckinghamshire, Oxfordshire, Northamptonshire and Warwickshire. Although the West Coast Main Line is the faster and original main line between the two cities, the Chiltern Main Line remains popular due to its more direct route between its two termini; it thus complements the West Coast Main Line by providing an additional link between Britain's two largest cities, as well as a useful commuter route for the small towns near both ends of the route. It is one of the Snow Hill Lines. The line is not electrified, and is operated by Class 150 (near Birmingham), Class 165 (near London) and Class 168 (between the cities) diesel multiple units.