Train

A train is a form of rail transport consisting of a series of vehicles propelled along a rail track to transport cargo or passengers. Motive power is provided by a separate locomotive or individual motors in self-propelled multiple units. Although historically steam propulsion dominated, the most common modern forms are diesel and electric locomotives, the latter supplied by overhead wires or additional rails. Other energy sources include horses, rope or wire, gravity, pneumatics, batteries, and gas turbines. Train tracks usually consists of two, three or four rails, with a limited number of monorails and maglev guideways in the mix. ... There are various types of trains that are designed for particular purposes. A train can consist of a combination of one or more locomotives and attached railroad cars, or a self-propelled multiple unit (or occasionally a single or articulated powered coach, called a railcar). ... From the 1910s onwards the steam locomotives began to be replaced by less labour-intensive and cleaner (but more complex and expensive) diesel locomotives and electric locomotives, while at about the same time self-propelled multiple unit vehicles of either power system became much more common in passenger service. [Train. Wikipedia]