Tram

A tram (also known as a tramcar; a streetcar or street car; and a trolley, trolleycar, or trolley car) is a passenger rail vehicle which runs on tracks along public urban streets and also sometimes on separate rights of way. Trams powered by electricity, which were the most common type historically, were under the classification of electric street railways. Trams also include horse railways which were widely used in urban areas before electrification.

Trams may also run between cities and/or towns (interurbans, tram-train), and/or partially grade separated even in the cities (light rail). Trams very occasionally also carry freight.

Trams are usually lighter and shorter than conventional trains and rapid transit trains. However, the differences between these modes of public transportation are often unclear. Some trams (for instance tram-trains) may also run on ordinary railway tracks, a tramway may be upgraded to a light rail or a rapid transit line, two urban tramways may be united to an interurban, etc.

Most trams today use electrical power, usually fed by a pantograph; in some cases by a sliding shoe on a third rail or trolley pole. If necessary, they may have several power systems. Certain types of cable car are also known as trams. Another power source is diesel; a few trams use electricity in the streets and diesel in more rural environments. Steam, petrol (gasoline), gas and animals have historically been used as power sources. Horse and mule driven trams do still occur.

Tramways are now included in the wider term "light rail", which also includes segregated systems. Some systems have both segregated and street-running sections, but are usually then referred to as trams, because it is the equipment for street-running which tends to be the decisive factor. Vehicles on wholly segregated light rail systems are generally called trains, although cases have been known of "trains" built for a segregated system being sold to new owners and becoming "trams".