This International Recommendation specifies the metrological and technical requirements applicable to compressed gaseous fuel measuring systems for vehicles, at type approval, initial verification and subsequent verifications. It also provides requirements for the approval of constituent elements of the measuring systems (meter, etc.). Measuring systems for liquid petroleum gas do not fall within the scope of this Recommendation, but within that of OIML R 117 as the fluid is in a liquid state. In general, the measuring systems that are covered by this Recommendation are intended for the refueling of motor vehicles, small boats, and aircraft with compressed natural gas. Applications with other compressed gaseous fuels are covered. Application to other vehicles, for instance trains, are also possible. Member States are free to limit the applications subject to national legal metrology control. In principle, this Recommendation applies to all measuring systems fitted with a meter as defined in T.1.1 (continuous measurement), whatever may be the measuring principle of the meters or their application. This Recommendation is not intended to prevent the development of new technologies. According to the state of the art, this Recommendation is intended for measuring systems that provide mass indications. If further evolution of technology allows indications in other units of measurement, this Recommendation will have to be revised.