This part of ISO 11992 specifies the parameters and messages for electronically controlled braking systems other than systems for braking and running gear (i.e. steering, suspension and tyres), to ensure the interchange of digital information between road vehicles with a maximum authorized total mass greater than 3 500 kg and their towed vehicles, including communication between towed vehicles. The objective of the data structure is to optimize the use of the interface, while preserving a sufficient reserve capacity for future expansion.