Road tank vehicles transporting liquefied gas brought into service in the UK must meet the vehicle and service equipment construction requirements of the European agreement concerning the international carriage of dangerous goods by road. These requirements include at least three mutually independent closures mounted in series, and spring-loaded safety valves.
Tank vehicles and shells must be certified as meeting the requirements prior to entering into service for the first time. Tank vehicles must pass an annual inspection thereafter to ensure they remain fit for service and tank shells are subject to periodic inspection requirements.
There is no requirement within UK or international law for all tankers to be equipped with double hulls.
The requirements for double-hulling of such ships are based upon the type of cargo carried and as such there is no expectation that at a specific date the entire fleet of UK registered tankers will be so equipped.