This part of ISO/TR 14179 presents a means for determining the thermal load carrying capacity of gears that includes measurement on original gear units under practical conditions. This takes the form of either measurement of the power loss, heat dissipation or both, or, in the case of splash-lubricated gear units, the determination of the quasi-stationary temperature in the oil sump. The methods of calculation for all individual components of power loss and heat dissipation described in this part of ISO/TR 14179 are to be regarded as an alternative method.