The recommendation from IMO, as described in MSC.1/ Circ 1471(see below text) concerning leak-tightness checks and labeling have been adopted as a requirement.
"The shipper should provide a signed certificate or declaration that the vehicle fuel system, as offered for carriage, has been checked for leak-tightness and the vehicle is in proper condition for carriage prior to loading. In addition, the shipper is to mark, label or placard each vehicle, after it has been checked for leak-tightness and that it is in proper condition for carriage. During loading, the crew should check each vehicle for the shipper's markings."