This paper provides a roadmap for engineers wanting to apply SAE J-1939 to applications requiring high input/output counts and a high number of nodes. The differences of the various SAE “J” specifications for CAN will be discussed. There are brief descriptions of some of the terms and standards involved. Coverage of the design parameters and decisions that have to be made to develop a survivable system will be outlined. The decision process on the use of “Proprietary” and “Registered J-1939 is analyzed. Methods of achieving high flexibility as well as the future directions of J-1939 and typical applications are addressed in relation to engineering flexibility, product standardization, parts rationalization, service, and customer convenience.