A tram (in North America streetcar or trolley) is a rail vehicle that runs on tramway track public urban streets; some include segments of segregated right-of-way. The lines or networks operated by tramcars as public transport are called tramways or simply tram/streetcar. Historically the terms electric street railways and trolley (not meaning trolleybus) were also used in the United States. In the United States, the term tram has sometimes been used for rubber-tired trackless trains, which are unrelated to other kinds of trams.