The ‘family’ of RO/RO vessels can be expanded to include ferries which frequently carry a mixture of passengers as well as wheeled cargo, and vessels such as ‘railway’ or ‘train-ferries’, complete with rail track on decks to accommodate railway carriages and trucks, equipped with a sophisticated and sensitive ballasting system to enable the ships’ rail tracks to be safely and securely connected to the shore rail system. Another variety of RO/RO is the Car Carrier, ‘Pure Car Carriers‘ (or ‘PCC’S‘ as they are usually known) being specially designed with fixed decks and sophisticated ventilation system for the carriage of motor cars and nothing else. A development from this basic design is the ‘Pure Car and Truck Carrier‘ – the ‘PCTC‘ – in which the clearances of some decks can be adjusted to accommodate larger vehicles as well as cars. All lend themselves to highly efficient cargo-handling, during which an entire cargo of perhaps 5,000 motor cars can be driven on or off in a matter of hours. In chartering terms this is another specialised market, the main players being the liner and ferry operators and the automotive industries. We have already read of general-cargo vessels fitted with heavy-lift derricks. But there are certain articles moved by sea that are far too heavy for even heavy-lift derricks capable of sustaining weights of up to 450 tonnes. To meet this demand, there are specialised Heavy-Lift ships. There are basically two types of heavy -lift vessel, the smaller capacity unit reliant on lifting cargo on and off with its own gear, and capable of sustaining lifts of around 600 tonnes unit weight. These ships are generally of a conventional appearance and from outside look very much like a multi-purpose ship. A series of ships capable of lifting 640-tonne pieces is already operating but these will be dwarfed by a series currently (2003) under construction that will be able to lift individual cargo units of up to 1,600 tonnes.