Ro-Ro

Roll On-Roll Off - Ships and Concepts

(Ro-Ro) shipping refers to the carriage of wheeled cargo,

, as well as general cargo on wheels on board of vessels that are provided with a ramp allowing the cargo to be rolled (instead of lifted) on board, and vice versa. Although the concept of Ro-Ro is particularly well established in passenger- and freight ferry short sea trades, the focus of this publication is on the carriage of breakbulk cargo in deep-sea trades. Nevertheless, occasional reference may be made to the former types of transport to clarify differences with the latter.

The defining characteristics of the Roll-on Roll-off concept can be summarised as follows: Ro-Ro vessels are flexible general cargo ships with through (horizontal) cargo decks as opposed to (vertical) holds. They usually have multiple decks, accessible through doors in the bow, stern or side of the vessel. These doors have an integral ramp so that cargo can be rolled (driven) on board without the need for shore-side infrastructure. Inside the ship, access between the decks can be enhanced by a combination of hoistable/liftable decks, internal ramps and elevators. In the main, the weather deck of Ro-Ro ships (onto which cargo can be rolled and/or lifted on and off) has no hatch openings. Ro-Ro capacity is often expressed in lane metres (lm), for which however there is no standard (width) formula. The actual lane metres used depend, voyage-by-voyage, on space taken by other than Ro-Ro cargo.

The main types of deep-sea Ro-Ro ships are:

- Full Roll on-Roll off cargo vessels (Full Ro-Ro)

- General Cargo ships with (auxiliary) Ro-Ro access (GenRo)

- Container vessels with Ro-Ro capacity (ConRo)

- Pure Car Carriers (PCC) and Pure Car and Truck Carriers (PCTC)

Ro-Ro cargo

- wheeled: self sustained units such as cars, trucks, rolling equipment and the like

- on wheels (wheelable): any kind of breakbulk cargo that is mobilised, i.e. placed on a trailer-type unit and then towed on board.

However, unitised general cargo may also be rolled on board with such equipment as roll trailers and/or forklift trucks and then stowed directly on the decks.

Ro-Ro vessel types

The carriage of cargo on a Roll on-Roll off basis can be considered as a specialised offshoot from traditional conventional shipping. On occasions, the addition of Ro-Ro capability is indeed complementary to the vessel’s predominantly general cargo character.

The Ro-Ro segment has developed into further specialisations as seen by its dominance of the short-sea passenger and car ferry market in particular, an area not under discussion here.

The Ro-Ro concept has also been taken up by the deepsea trades. Currently a fairly wide-range of Ro-Ro capable vessels is trading and incorporates various features designed to promote maximum ship and cargo flexibility. This can certainly be said for the purest form of Ro-Ro: the “Pure Car Carrier” (PCC) and “Pure Car Truck Carrier” (PCTC).

Full Roll on-Roll off cargo vessels (Full Ro-Ro)

Such ships are (un)loaded purely through the vessels’ stern ramp(s). They will not have hatches on the weather deck, although access to this may be possible through an internal ramp or elevator. Some ships may only have a single main deck, above which is the weather deck. A Ro-Ro vessel will often carry along its own handling equipment such as forklift trucks and the like to allow for quick and easy loading. The “full” or dedicated Ro-Ro vessel employed in deepsea trades can range from as little as 2,000-dwt up to just over 40,000 dwt.

General Cargo/Conventional vessels with Ro-Ro access (GenRo)

This is where the general cargo vessel also incorporates some form of Ro-Ro access, which could be through a (quarter) stern ramp or a side ramp. Access will be limited to perhaps only one deck or hold, and unlike the full Ro-Ro ship there will be no internal ramp/elevator system. The vast majority of vessels that fall under this category range between 2,000 and 28,000 dwt.

Container/Ro-Ro vessels (ConRo)

These ships are a combination of the two shipping concepts. Access for the wheeled and wheelable cargo is generally through a (an angled) stern ramp, leading to the vessel's garage decks only. The remaining holds, accessible through cargo hatches, are either provided with cell guides or are otherwise suitable for containers. A variation is full Ro-Ro on the main deck and containers on the weather deck. Deepsea ConRo's tend to be larger than GenRo's, starting at around 20,000-dwt and going up to nearly 52,000 dwt.

Pure Car Carrier (PCC) and Pure Car and Truck Carrier (PCTC)

The ultimate embodiment of the deep-sea Ro-Ro concept, these ships are recognisable for sitting high in the water and increasingly, their rounded appearance particularly forward. The height is not surprising as they may incorporate more then ten decks!

- The PCC, also described as a floating multi-storey car park is indeed adapted to carrying cars only. It is of a lighter construction than Ro-Ro vessels in general and has lower deck heights. The hull will be slimmer and more streamlined than other Ro-Ro cargo vessels allowing for greater fuel efficiency while sailing at the faster speeds needed for time sensitive deliveries demanded by the car industry. As the PCC has been designed to carry evenly distributed unit (car) loads of around 1 ton each, it is not well suited to carrying breakbulk cargo.

- The PCTC is designed for the carriage of both cars and "high-and-heavy", an industry term for such rolling stock as buses, trucks, agricultural machinery (including harvesters) and road building and construction equipment. Usually fitted with a heavy-duty ramp, they are equally able to take machinery, heavy lifts and other project cargoes as well as nearly any other breakbulk cargo on wheels, making them the ultimate car carrier-general cargo-heavy lift-Ro-Ro hybrid. Some decks of the PCTC are strengthened and the decks above these can be raised to accommodate oversized cargoes.

- The application of a quarter stern ramp plus another (generally starboard) side door and ramp is virtually universal for the PCC and PCTC, as well as the fact that they take no cargo on the weather deck. The side door/ramp has an accompanying internal elevator to lift the cars to the relevant deck. PCTCs vary in size but for deep-sea trades are mostly found in the 15,000-35,000-dwt range (with exceptions on either side). Their carrying capacity given in CEU (car equivalent units) has rapidly increased over the last few years. Currently a number of 8,000 CEU capacity PCTCs (meanwhile also described LCTC, Large Car Truck Carriers), boasting some 14 decks are under construction.