This standard concerns tankers for the transport by rail or road of liquid products and used (in addition to their functions as carriers), as measuring instruments subject to national metrological controls, and tankers whose effective volumes must be known in order to determine their maximum permissible filling loads for reasons of transport safety. 1.2. A mobile tanker to be considered as a volume-measuring instrument shall comply with the requirements of point 4 of this standard. Note: The value of the nominal capacity of a tank cannot be used directly in official operations (commercial transactions), as the volume of the contained product varies with temperature (see Annex 1). 1.3. Tankers may be considered as measuring instruments for liquids of which the viscosity does not exceed 17 mPa · s at measurement temperature. 1.4. The verification methods and equipment described in this standard are examples. In practice, other verification methods and equipment may be used, provided that they give results of equal accuracy.