There is little doubt that there is a desire for transit standards to assist in decision making across the entire range of planning, designing, constructing and operating the transit system. Even discussing this broad range is difficult, since both the breadth and depth of potential application areas for standards is of such scale as to be outside the expertise of any single individual. A general classification scheme is developed for structuring the discussion which distinguishes between standards for different transit modes, as well as between fixed facilities and vehicles.Transit standards are divided into input standards -- relating to those system attributes under the control of the planner, designer, or operator -- and output standards -- which reflect the ultimate objectives which the system is designed to satisfy. Examination of standards related to rail transit reveal some standardization accepted in practice, though it is not clear whether this acceptance is because of demonstrated benefits or simply conventional practice. Some areas can be identified where standardization might result in cost savings.