Roll-on/roll-off (RORO or ro-ro) ships are cargo ships designed specifically to transport wheeled cargo, such as cars, motorcycles, trucks, semi-trailer trucks, buses, trailers and railroad cars, which are moved directly onto and off the ship by their own wheels or on a platform vehicle such as a self-propelled modular transporter. This is in contrast to lift-on/lift-off (LoLo) vessels, which rely on cranes to load and unload cargo.
RORO vessels typically have a multistorey carpark-like cargo hold layout and use either built-in or dock-based linkspans (ramps) or ferry slips that allow the cargo to be efficiently loaded on and off the vessel when in port. The cargo doors and/or ramps may be located in the stern, bow or portsides, or any combination thereof. While smaller ferries that operate short distances across rivers and other waterbodies often also have built-in ramps, the term RORO is generally reserved for large seagoing vessels owned/chartered by the automotive industry for export shipping.
Description
Types of RORO vessels include ferries, cruiseferries, cargo ships, barges, and RORO service for air/railway deliveries. New automobiles that are transported by ship are often moved on a large type of RORO called a pure car carrier (PCC) or pure car/truck carrier (PCTC).
Elsewhere in the shipping industry, cargo is normally measured by tonnage or by the tonne, but RORO cargo is typically measured in lanes in metres (LIMs). This is calculated by multiplying the cargo length in metres by the number of decks and by its width in lanes (lane width differs from vessel to vessel, and there are several industry standards). On PCCs, cargo capacity is often measured in RT or RT43 units, based on a 1966 Toyota Corona, the first mass-produced car to be shipped in specialised car-carriers and used as the basis of RORO vessel size. One RT is approximately 4 m of lane space required to store a 1.5 m wide Toyota Corona. Cargo capacity may also be measured in car-equivalent units (CEU).
The largest RORO passenger ferry is , a cruise ferry that entered service in September 2007 for Color Line. Built in Finland by Aker Finnyards, it is long and wide, and can carry 550 cars, or 1,270 lane meters of cargo.
The RORO passenger ferry with the greatest car-carrying capacity is , owned by Irish Ferries. Ulysses entered service on 25 March 2001 and operates between Dublin and Holyhead. The 50,938 GT ship is long and wide, and can carry 1,342 cars/4,101 lane meters of cargo.
Car carriers
The first cargo ships specially fitted for the transport of large numbers of cars came into service in the early 1960s. These ships still had their own loading gear and so-called hanging decks inside. They were, for example, chartered by the German Volkswagen AG to transport vehicles to the U.S. and Canada. During the 1970s, the market for exporting and importing cars increased dramatically and correspondingly also did the number and type of ROROs .
In 1970 Japan's K Line built Toyota Maru No. 10, Japan's first pure car carrier, and in 1973 built European Highway, the largest pure car carrier (PCC) at that time, which carried 4,200 automobiles. Today's pure car carriers and their close cousins, the pure car/truck carrier (PCTC), are distinctive ships with a box-like superstructure running the entire length and breadth of the hull, fully enclosing the cargo. They typically have a stern ramp and a side ramp for dual loading of thousands of vehicles (such as cars, trucks, heavy machinery, tracked units, Mafi roll trailers, and loose statics), and extensive automatic fire control systems.
The PCTC has liftable decks to increase vertical clearance, as well as heavier decks for "high-and-heavy" cargo. A 6,500-unit car ship, with 12 decks, can have three decks which can take cargo up to with liftable panels to increase clearance from on some decks. Lifting decks to accommodate higher cargo reduces the total capacity. These vessels can achieve a cruising speed of at eco-speed, while at full speed can achieve more than .
, the largest LCTC is MV Glovis Leader of approximately 10,800 units. Other large ships are the Höegh Aurora class, the inaugural vessel of a planned class of twelve, each with a capacity of 9,100 CEU. Meanwhile, the Marine Design & Research Institute of China (MARIC) is developing a new vessel class with a capacity of 12,800 CEU. The design has received Approval in Principle (AiP) from Lloyd's Register, which was granted in June 2024.
The car carrier , belonging to Nippon Yusen Kaisha, built in 2008 with a capacity of 6,200 cars, is the world's first partially solar-powered ship.
Seaworthiness
The seagoing RORO car ferry, with large external doors close to the waterline and open vehicle decks with few internal bulkheads, has a reputation for being a high-risk design, to the point where the acronym is sometimes derisively expanded to "roll on/roll over". An improperly secured loading door can cause a ship to take on water and sink, as happened in 1987 with Herald of Free Enterprise. Water sloshing on the vehicle deck can set up a free surface effect, making the ship unstable and causing it to capsize. Free surface water on the vehicle deck was determined by the court of inquiry to be the immediate cause of the 1968 capsize of in New Zealand. It also contributed to the wreck of .
Despite these inherent risks, the very high freeboard improves the seaworthiness of these vessels. For example, the car carrier Cougar Ace listed 60 degrees to its port side in 2006, but did not sink, since its high enclosed sides prevented water from entering.
In late January 2016 was listing off France after cargo shifted on the ship. Salvage crews secured the vessel and it was hauled into the port of Bilbao, Spain.
RORO variations
+ RORO variations VariationDecscription ConRO The ConRo (or RoCon) vessel is a hybrid of a RORO and a container ship. This type of vessel has a below-deck area used for vehicle storage while stacking containerized freight on the top decks. ConRo ships, such as the of the Atlantic Container Line, can carry a combination of containers, heavy equipment, oversized cargo, and automobiles. Separate internal ramp systems within the vessel segregate automobiles from other vehicles, Mafi roll trailers, and break-bulk cargo. LMSR Large, Medium-Speed Roll-on/Roll-off (LMSR) refers to several classes of the United States' Military Sealift Command (MSC) roll-on/roll-off type cargo ships. Some are purpose-built to carry military cargo, while others are converted. RoLo A RoLo (roll-on/lift-off) vessel is another hybrid vessel type, with ramps serving vehicle decks but with other cargo decks only accessible when the tides change or by the use of a crane. ROPAX ROPAX (roll-on/roll-off passenger) describes a RORO vessel built for freight vehicle transport along with passenger accommodation. Technically this encompasses all ferries with both a roll-on/roll-off car deck and passenger-carrying capacities; many of those with facilities for more than 500 passengers may be described as cruiseferries.
History At first, wheeled vehicles carried as cargo on oceangoing ships were treated like any other cargo. Automobiles had their fuel tanks emptied and their batteries disconnected before being hoisted into the ship's hold, where they were chocked and secured. This process was tedious and difficult, and vehicles were subject to damage and could not be used for routine travel.
An early roll-on/roll-off service was a train ferry, started in 1833 by the Monkland and Kirkintilloch Railway, which operated a wagon ferry on the Forth and Clyde Canal in Scotland.
Invention
The first modern train ferry was , built in 1849. The Edinburgh, Leith and Newhaven Railway was formed in 1842 and the company wished to extend the East Coast Main Line further north to Dundee and Aberdeen. As bridge technology did not yet support the crossing over the Firth of Forth, which was roughly across, a different solution had to be found, primarily for the transport of goods, where efficiency was key.
The company hired the up-and-coming civil engineer Thomas Bouch, who argued for a train ferry with a roll-on/roll-off mechanism to maximise the efficiency of the system. Ferries were to be custom-built, with railway lines and matching harbour facilities at both ends to allow the rolling stock to easily drive on and off. To compensate for the changing tides, adjustable ramps were positioned at the harbours and the gantry structure height was varied by moving it along the slipway. The wagons were loaded on and off using stationary steam engines.
Although others had had similar ideas, Bouch was the first to put them into effect, and he did so with an attention to detail (such as design of the ferry slip) which led a subsequent President of the Institution of Civil EngineersGeorge Parker Bidder; not to be confused with the lawyer (his son) who represented Bouch at the Tay Bridge Inquiry to settle any dispute over priority of invention with the observation that "there was little merit in a simple conception of this kind, compared with a work practically carried out in all its details, and brought to perfection."
The company was persuaded to install this train ferry service to transport goods wagons across the Firth of Forth from Burntisland in Fife to Granton. The ferry itself was built by Thomas Grainger, a partner of the firm Grainger and Miller.
The service commenced on 3 February 1850. It was called "The Floating Railway" and intended as a temporary measure until the railway could build a bridge, but no bridge was opened until 1890, its construction delayed in part by repercussions from the catastrophic failure of Thomas Bouch's Tay Rail Bridge.
Expansion Train ferries were used extensively during World War I. From 10 February 1918, high volumes of railway rolling stock, artillery and supplies for the Western Front were shipped to France from the "secret port" of Richborough, near Sandwich on the south-east coast of England.
Three train ferries were built, each with four railway tracks on the main deck, to allow up to 54 railway wagons to be shunted directly on and off the ferry. These ferries could also be used to transport motor vehicles along with railway rolling stock. Later that month a second train ferry route was established from the Port of Southampton on the south coast. In the first month of operations at Richborough, 5,000 tons were transported across the English Channel, and by the end of 1918 nearly 261,000 tons had been transported.
These ferries had many advantages over conventional shipping in World War I. It was much easier to move large, heavy artillery and tanks on ferries, as opposed to repeated loading and unloading of cargo. Manufacturers could load tanks, guns and other heavy items for shipping to the front directly onto railway wagons, which could be shunted on to a train-ferry in England and then shunted directly onto the French railway network, with direct connections to the front lines; thus many man-hours of labour were avoided.
A contemporary analysis found that to transport 1,000 tons of war material from the point of manufacture to the front by conventional means involved the use of 1,500 labourers, whereas when using train-ferries that number decreased to around 100 labourers. This was of utmost importance, as by 1918 the British railway companies had a severe labour shortage, as hundreds of thousands of skilled and unskilled labourers were away fighting at the front. The increase in heavy traffic because of the war effort meant that economies and efficiency improvements in transport had to be made wherever possible.