Place of light rail transit in the family of transit modes. Paper presented at the National Conference of the Transportation Research Board, Philadelphia, June 1975.

The paper attempts to clarify concepts and terminology of urban transit systems. Modes are defined by type of right of way, system technology, and type of service and operation. Right-of-way is shown to be the most important single feature determining mode performance and cost. Advantages of partial or full separation of transit from surface traffic are defined. The basic features of system technology are analyzed.