Definition: Trackless Trolley / Electric Trolley Bus

A trolley bus or trackless trolley is an electrically powered bus that draws its power from a pair of parallel overhead wires by means of two trolley poles. (Electric rail vehicles require only one overhead wire as they complete the electrical circuit by returning power through rails. Trolley buses require a second wire to complete the circuit.) Trolley buses became popular as a transitional step to replace streetcar systems on which the cars and track and track were worn out but which had a serviceable and not-fully-depreciated power distribution system. In the years before diesel powered buses were perfected, trolley buses provided more capacity and superior operating characteristics to gasoline powered buses. Most were replaced by diesel buses after the first generation of vehicles came to the end of their operating life. However, they have been retained by a few cities, notably San Francisco, Seattle, and Vancouver (BC), where their superior hill climbing ability and emission free operation are valued.

Two electric trolley buses -- one contemporary and one from the late 1940s -- in Vancouver, BC.

Today considerable confusion exists over the term trolley bus or trackless trolley, as people often assume the terms refer to the ubiquitous rubber tired buses that are decorated to look somewhat like traditional streetcars. However, these “bus trolleys” are quite different from trolley buses or trackless trolleys.