The RO/RO (Roll on – roll off) vessel can vary from a very simple river ferry design used only in inland waters to some of the most sophisticated vessels afloat today including passenger ferries with leisure facilities approaching those of cruise vessels. For areas of the world possessing only limited port facilities, the RO/RO ship with its ‘self-sustaining’ ability to load and discharge provides an ideal mode of transport. A typical deepsea RO/RO vessel is usually equipped with its own fork-lift trucks and tractors and, perhaps a crane or two, and is capable of handling from alongside a whole range of wheeled vehicles as well as palletised and containerised goods. Access to the interior of RO/RO vessels is usually via a stern ‘ramp‘ which, in modern ships is capable of sustaining very heavy loads of up to several hundred tonnes, and sometimes of being ‘slewed‘ around and raised or lowered to suit whatever berth access may be available. Once inside a RO/RO vessel, ramps or lifts lead up or down to various deck levels where a whole variety of goods may be stowed, decks and tank-tops being strengthened to take heavy loadings. Every commodity that lends itself to transportation via a RO/RO or a LO/LO (‘Lift On/Lift Off’) system may be carried on this type of vessel, which can sustain all kinds and most sizes of rolling stock and merchandise that can be placed on wheels. Because RO/RO vessels form an extension to the natural road transportation environment for wheeled vehicles, particularly for articulated lorries which can unhitch and deposit their trailer on board, certain RO/RO ships are sometimes referred to as ‘trailer-carriers‘, their capacity for the carriage of these trailers being described in terms of length of available ‘lane metres‘. The width of a ‘lane’ varies according to the construction of an individual ship, though these must be a minimum of just over 2.5 metres (8 feet), to suit standard vehicle and container dimensions. To allow adequate space for lashing and securing cargo, however, the realistic minimum of a lane should be 3 metres (10 feet).