A tram (also known as tramcar; and in North America known as streetcar, trolley or trolley car) is a rail vehicle which runs on tracks along public urban streets, and also sometimes on a segregated right of way. The lines or networks operated by tramcars are called tramways. Tramways powered by electricity, the most common type historically, were once called electric street railways (mainly in the USA). However, trams were widely used in urban areas before the universal adoption of electrification; other methods of powering trams are listed below under "History".