This International Standard establishes a classification of, and lays down the requirements for self-propelled water craft employed in the pilot servicing of merchant ships in closed waters, estuaries and open-sea roadsteads. It has been drawn up with a view to promoting that sector of international trade which involves merchant ships; to improving working conditions and to increasing the safety of labour in water transport; and to standardizing a number of terms used in the design and operation of vessels of the service and auxiliary fleets. The water craft employed mainly in pilotage of merchant ships by leading may be relieved of adhering to these requirements completely or partially at the discretion of the competent authorities. The applicability of the requirements of this International Standard to pilot craft navigating under a navy flag is determined by the competent authorities of the relevant country.