This International Standard cancels and replaces ISO Technical Report ISO/TR 4004-1975. Applies to the principal driven axle(s) of tractors and to macinery, including self-propelled machinery, uesd in fields for row-crops. It does not apply to tractors of special types, to walking tractors, to single-axle motor-driven machines, to two-wheeled propulsion units, or to agricultural machinery of special types.