By issuing in the Official Journal of the European Union (L285 / 1) The United Nations Economic Commission for Europe (UNECE) has issued uniform conditions for the approval of the special equipment of vehicles in their respective countries Propulsion system liquefied gases, as well as approval for the installation of this equipment [2016/1829] today.

Requirements, conditions, application procedures as well as approval distribution can be found in Parts I and II of the detailed documented rules in the EUR-Lex under: https://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1403857575017&uri=CELEX:42016X1829

as well as on the website of

UNECE: https://www.unece.org/trans/main/wp29/wp29wgs/wp29gen/wp29fdocstts.html