Roll-on/roll-off ships

The modern roll-on/roll-off ship can trace its origins back more than one hundred years to the early days of the steam train. Ships were specially designed to take trains across rivers which were too wide for bridges: the ships were equipped with rails, and the trains simply rolled straight on to the ship, which sailed across the river to another rail berth where the train would roll off again. An example is the Firth of Forth ferry in Scotland, which began operations in 1851.

It was not until the Second World War, however, that the idea of applying the ro-ro principle of road transport became practicable - and was used in constructing the tank landing craft used at D-Day and in other battles. The principle was applied to merchant ships in the late 1940s and early 1950s. It proved to be extremely popular, especially on short-sea ferry routes, encouraged by technical developments on land as well as sea, notably the increase in road transport.

For the shipper, the ro-ro ship offered a number of advantages over traditional ships, notably speed. As the name of the system implies, cars and lorries can drive straight on to a ro-ro ship at one port and off at the port on the other side of the sea within a few minutes of the ship docking.

Ro-ro ships also integrate well with other transport development, such as containers, and the use of Customs-sealed units (first introduced in the late 1950s) has enabled frontiers to be crossed with the minimum of delay, thereby further increasing speed and efficiency for the shipper.

Cars going on board a ferry at the port of Calais(Left)

 

The vehicle deck of a ro-ro ship runs the entire length of the vessel. This makes loading and unloading a simple matter – but it does present a number of safety issues, which are unique to this type of ship.(Right)

Ro-ros have also proved extremely popular with holiday makers and private car owners and have significantly contributed to the growth of tourism. Until the early 1950s someone wishing to take his car from one country to another by sea had to get it loaded into the ship's hold by crane, a time-consuming and expensive process. The development of the ro-ro car ferry changed all that and many ports boomed as a result.

In the United Kingdom, Dover's first pair of drive-on berths was opened in 1953. Until then the port had handled only 10,000 crane-loaded cars each year and forecasts that the berths would enable the port to handle ten times that many must have seemed decidedly optimistic. But the 100,000 figure was exceeded in the first year and by 1985 Dover was handling over 2.5 million vehicles and units through nine ro-ro berths. By 1994 the total had risen to more than 4.5 million.

Ro-ro ferries in the port of Dover

By 1994 around 4,600 ro-ro ships were in operation around the world: They are particularly popular in Europe, and trading patterns reflect this. Whereas pure container ships are to be found in large numbers operating between Europe and North America, Europe and Japan and Japan and North America, ro-ros operate primarily between Europe and North America and Europe and the Middle East, although there is an important trade between North America and the Caribbean.

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 ro-ro 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.

Despite their commercial advantages, the roll-on/roll-off ship concept has not been without problems. In particular, the huge open car deck and the presence of doors near the waterline presents points of weakness that need to be carefully considered.