This International Standard specifies safety requirements for auto-guidance systems used in agricultural tractors and self-propelled agricultural machines. It is applicable to auto-guidance systems which are factory installed as an integral part of the tractor or self-propelled machine as well as systems designed to be retrofitted to equipment after such equipment has left the control of the manufacturer. It is not applicable to guidance systems used in tractors or self-propelled machines that do not require an on-board operator for primary control of the tractor or self-propelled machine. This International Standard does not specify requirements necessary to ensure the integrity of the complex electronic control system which can be an integral part of the auto-guidance system. Such requirements are dealt with in other International Standards which address complex electrical/electronic vehicle control systems. When requirements of this International Standard are different from those which are stated in a machine specific standard, the requirements of the machine specific standard take precedence over the requirements of this International Standard. This International Standard is neither applicable to tractors and self-propelled machines which were manufactured with an auto-guidance system before the date of publication of this International Standard, nor to self-contained auto-guidance retrofit systems which were individually placed on the market before the date of publication of this International Standard. NOTE Specific road traffic regulations can impose additional requirements for auto-guidance systems.