SAE J 1939-01 On-Highway Equipment Control and Communication Network specifies the minimum set of SAE J1939 documents that define the Truck and Bus Control and Communications Vehicle Network as it applies to on-highway equipment. Vehicles covered include all on-highway straight trucks and road trains. A road train consists of one towing vehicle (tractor), and one or more towed vehicles (trailers and dollies). Dolly axles within the road train are considered to be towed vehicles. It is the intention of the SAE J1939 family of recommended practices to all electronic devices to communicate with each other by providing a standard architecture. SAE J 1939-01 describes the particular set of SAE J1939 documents used to implement an open interconnect system for electronic systems in a heavy-duty on-highway vehicle.