The purpose of these recommended practices is to provide an open interconnect system for electronic systems. It is the intention of these recommended practices to allow electronic devices to communicate with each other by providing a standard architecture.
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 vehicle(s) (trailers and dollies). Dolly axles within the road train are considered to be towed vehicles.