Class III,Ships engaged only on voyages in the course of which they are at no time more than 70 miles by sea from their point of departure nor more than 18 miles from the coast of the United Kingdom, and which are at sea only in favourable weather and during restricted periods,
Class IV,Ships engaged only on voyages in Category A, B, C or D waters,
Class V,Ships engaged only on voyages in Category A, B or C waters,
Class VI,Ships engaged only on voyages, carrying not more than 250 passengers, to sea or in Category A, B, C or D waters, in all cases in favourable weather and during restricted periods, in the course of which the ships are at no time more than 15 miles, exclusive of any Category A, B, C or D waters, from their point of departure nor more than 3 miles from land,
Class VI(A),Ships carrying not more than 50 passengers for a distance of not more than 6 miles on voyages to or from isolated communities on the islands or coast of the United Kingdom and which do not proceed for a distance of more than 3 miles from land,