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Further Reading

Variations on the Ro-Ro Theme

Today the world ro-ro fleet can be subdivided into a number of different types. They include ships designed to carry freight vehicles only; to carry a combination of containers and freight vehicles and to transport cars without passengers. There are various other types and freight-only roro ships form about two thirds of the world ro-ro fleet at present. However, the best known ro-ro ships are ferries designed to transport commercial vehicles and private cars, together with large numbers of passengers, usually on short voyages.

Most ships of the Ro-Ro type, i.e. ships for the transportation of wheeled vehicles which may be driven into, and out of the ship, respectively, or which are adapted to take care of containers or other standardized cargo units which are handled by fork lift trucks or similar transportation means, are usually provided with a single deck only. Ships having two or more decks are provided with lifts for transferring the cargo vertically between the decks, or has built-in linclined ramps, making it possible to drive from one deck to an other. Both arrangements require a considerable amount of space, and especially the lift arrangements are expensive. The handling of the cargo in the vertical direction will further take more time than the driving on-board.

• Sto-Ro (Stowable Ro-Ro) -- Contrary to the Ro-Ro, no cargo remains on wheels but is directly loaded onto vessel decks. The stowage is similar to an open Load-on/Load-off (Lo-Lo) vessel; however, the cargo is brought on board either over a stern/bow quarter ramp or through a side port door. Vessel operations can turn to this concept of cargo handling as a means of combining the undoubted handling ad-vantages of the Ro-Ro (improved turnaround times) with the efficiency of a Lo-Lo (increased utilization of a ship's cubic capacity).
• Float-On/Float-Off -- A heavy deck semi-submersible vessel designed to permit oversized indivisible cargo being floated into position for deck stowage. The reverse procedure is used at the destination port where the load is floated from the submerged deck that is ballasted down for the outturn. The vessel travels with its deck and load above the water.
• Trot-On/Trot-Off -- Ro-Ro conversion or version in which vessel trailer decks are transformed into modern cattle pens capable of accommodating in excess of 2,000 animals. New installations include provision of fresh water through evaporation and increased tankage "barns" for 1,600 cubic meters of hay or straw and an air circulation plant.
• Combination Container and Ro-Ro Vessels -- This design allows for flexibility of operation by incorporating container and other wheeled cargo handling capability. These vessels carry containers on and under deck forward and have a stem ramp with tween decks for the carriage of Roll-on/Roll-off cargo in the aft underdeck area. The Ro-Ro cargo may consist of over-sized pieces such as construction equipment, i.e., bulldozers and excavators, which are driven onto the vessel via the ramp. Containers can also be stowed on the Ro-Ro decks but are brought aboard on chassis and removed with forklift machines. If space and equipment is available the container can be left on its chassis during transport.
• A ferry is any vessel used to provide transportation only between places that are no more than 300 miles apart, and to transport only - passengers, or vehicles, or railroad cars, which are being used, or have been used, in transporting passengers or goods. The fundamental objective of ferry terminal design is to enable passengers and vehicles to proceed from the ferry to access a mode of continued travel. The internal layout of facilities reflects this concern for the convenience of passengers and their vehicles by providing simple and direct passenger/vehicle flow routes through the facilities. A tractor-trailer carried on a ferry with a container either loaded with cargo or empty will classify the vessel as a ferry and the goods within the trailer or container are looked upon as having arrived in the Customs territory by ferry.

Some current designs of roll-on/roll-off ferries for relatively short sea passages are twin-hulled designs. The engines are housed in the base of the hulls near the waterline, with power offtake shafts extending sternwards to the propulsors, which may comprise waterjets. These vessels are designed for high speeds, with small wetted hull areas to minimise drag from the water. Their loading decks are arranged to span the distance between the two hulls at as low a level as possible compatible with the seagoing ability required by the vessel and the rest of their superstructures are designed as far as possible with long low continuous lines to minimise aerodynamic drag and susceptibility to cross winds and to obtain the greatest possible stability for the vessel. A further design aim is to maximise cargo capacity.

RO-RO ships have also been developed to handle multicargoes, whereby they are enabled to transport different vehicles as a part of the cargo. In these ship types the cargo is transferred aboard by means of waggon and carriage pallets, which are carried along with the cargo to the port of destination. This method is applied particularly to transporting forest products. To increase loading flexibility, containers are also loaded on these pallets. Straddle carriers and trucks are also used for container handling. A high cargo space can be divided vertically in two or three sections by means of so-called hoistable car decks. The loading and unloading capacity of the ship is satisfactory. All in all, this method is, however, expensive on account of terminal facilities and special ship equipment. Space utilization and stowage efficiency are not good.

In 1992, the Washington State Ferry System decided three new Jumbo Mark II Ro-Ro Ferries were needed for its Bremerton and Bainbridge Island runs. The Jumbo Mark II was the first new auto ferries built for Washington State Ferries [WSF] in 20 years. While the name didn't show much imagination, it isn't entirely unjustified. The ferries are modern versions of the Jumbo Class ferries Spokane and Walla Walla. The Jumbo Mark II boats are designed to separate walk-on and auto traffic. The Mark II's hold 2,500 passengers, 500 more passengers than the Jumbos. The increase bumped their size up 20 feet. At 460 feet, they are the largest double-ended auto ferries in the world. While carring 500 more passengers, the auto capacity only went up by about 12, to 218. Passeger capacity was more important on the Bainbridge run, where the 2,000 passenger Jumbos were filling to capacity on the morning and evening commuter runs.

As of early 2006 the largest PCC in service was the MV Mignon, owned and operated by Wallenius Wilhelmsen Lines of Sweden, it can carry some 7,200 car equivalent unite [CEU]. The Mignon was the first of five Wallenius Boheme-class vessels to be stretched by 28 metres to 228 metres LOA. The lengthening results in making these the biggest car carriers in the world. The Mignon unloads cars, pleasure craft, etc and load export cars, trucks and haulers, predominantly for the US, at Port of Göteborg's Car Terminal. In addition to the five vessels stretched or to be stretched, Wallenius Lines have a newbuilding program of six pure car/truck carriers, three of 6,500 and three of 8,000 cars capacity.

Five of the ships will be built at the Daewoo Shipyard in Korea. The first two new vessels will have a cargo capacity of 6,700 cars and will be delivered at the end of 2006. The other three, each with a cargo capacity of 8,000 cars, will be delivered in late 2007 and early 2008. The ships will be operated by the subsidiary Wallenius Wilhelmsen Lines. The sixth ship, with a capacity of 6,400 vehicles, is being built at Hyundai Heavy Industries in Korea and will be operated by the Wallenius Korean subsidiary, EUKOR.

Wallenius Lines reached an agreement in early 2006 with Wilh. Wilhelmsen ASA regarding the sale of two LCTC newbuildings at Daewoo Shipbuilding & Marine Engineering. Each vessel has a capacity of 8,000 cars and is due for delivery in 2009. The Wallenius Lines newbuilding program now comprises eight vessels to be delivered between 2006 and 2008.