20th century. The technology uses magnets to levitate the train above the track, reducing friction and allowing higher speeds. The first commercial maglev train was an airport shuttle introduced in 1984 at Birmingham Airport in England. The Shanghai Maglev Train, opened in 2003, is the fastest commercial train service of any kind, operating at speeds of up to . Japan's L0 Series maglev holds the record for the world's fastest train ever, with a top speed of . Maglev has not yet been used for inter-city mass transit routes, with only a few examples in use worldwide as of 2021. Mine trains Mine trains are operated in large mines and carry both workers and goods. They are usually powered by electricity, to prevent emissions which would pose a health risk to workers underground. Militarized trains While they have long been important in transporting troops and military equipment, trains have occasionally been used for direct combat. Armored trains have been used in a number of conflicts, as have railroad based artillery systems. Railcar-launched ICBM systems have also been used by nuclear weapon states. Rack railway For climbing steep slopes, specialized rack railroads are used. In order to avoid slipping, a rack and pinion system is used, with a toothed rail placed between the two regular rails, which meshes with a drive gear under the locomotive. Funicular Funiculars are also used to climb steep slopes, but instead of a rack use a rope, which is attached to two cars and a pulley. The two funicular cars travel up and down the slope on parallel sets of rails when the pulley is rotated. This design makes funiculars an efficient means of moving people and cargo up and down slopes. The earliest funicular railroad, the Reisszug, opened around 1500. Freight trains Freight trains are dedicated to the transport of cargo (also known as goods), rather than people, and are made up of freight cars or wagons. Longer freight trains typically operate between classification yards, while local trains provide freight service between yards and individual loading and unloading points along railroad lines. Major origin or destination points for freight may instead be served by unit trains, which exclusively carry one type of cargo and move directly from the origin to the destination and back without any intermediate stops. Under the right circumstances, transporting freight by train is less expensive than other modes of transport, and