A transit bus is usually operated by an urban-suburban bus line, a governmental public transit agency, or a contractor.
A transit bus is normally used on public transit routes. It is typically equipped for city or frequent-stop suburban service, and features usually include a farebox, multiple doors, and efficient and spartan seating, as opposed to more comfortably appointed intercity buses or "express" buses, (although all would be considered mass transit).
As of 2014, an already-significant and increasing number of operations are using articulated buses on routes with heavy ridership. However, many experimental uses of double decker buses have not proved them to be practical in North American operatons other than for special sightseeing services in a few large cities (with the notable exceptions of GO Transit, Ottawa-Carleton Regional Transit Commission and the Regional Transportation Commission of Southern Nevada's The Deuce service).
Alternative fuels, most notably Compressed Natural Gas and Diesel-Electric Hybrid, have becoming an increasingly popular option since around the beginning of the 21st century. CNG and other natural-fuel options have become extremely popular in southern California due to strict emissions regulations.