A roll on roll off ship, or ro-ro, is a ship which has the ability to take on and release vehicles without making any special arrangements for the vehicles, hence the term "roll on, roll off."

The first roll on roll offs were established in the mid 19th century with the advent of the railroads system. Ships would be equipped with rails that could be connected to onshore rails. A train could then be loaded directly onto the ship and carried across bodies of water too wide for bridges.

It took nearly a hundred years for this technology to evolve and allow general road-ready vehicles to board ships. During World War II, the Army took notice of a Japanese innovation on their landing craft: a small bow ramp allowed troops to quickly abandon the boat and deploy to land. They began developing their own craft in this manner, and finally Andrew Higgins, a New Orleans boat builder, developed an amphibious landing craft that could come completely ashore without damaging itself. These Higgins boats were then improved by adding the bow ramp, and became very popular for deployment in the Pacific and European theaters.

Eventually, this technology was expanded to include landing craft for tanks and other combat vehicles. The Mk4, LCM, and LCI all served admirably in their task, and the roll-on, roll-off technology that supported them also began to see its first non-military use at industrial ports across the world. By the 1950s, Higgins and other boat manufacturers were developing larger ferries to transport large amounts of cars across wide watery expanses.

Generally, ro-ro ferries come in two flavors: the local domestic ferry, for carrying tourists and passengers across small bodies of water to continue their journey; and large commercial ferries, for transporting large amounts of cars across the oceans for private owners and dealerships. In 1994, over 4,500 of these such ferries were in operation, and carried nearly 20 million cars every year.

Sources

  • www.britannica.com/normandy/articles/landing_craft.html
  • www.oceansatlas.org/unatlas/uses/transportation_telecomm/ maritime_trans/shipworld/cargo_car/roro/ro_ro_ships.htm

RO/RO is an acronym (pronounced "row-row") for Roll-On / Roll-Off. It is sometimes written 'RORO' or 'RO-RO.' It is a term used to describe a particular characteristic or capability of ship, and sometimes of ports. Literally, it means the ability to load and unload cargo by driving vehicles directly onto and off of the ship. This is in contrast to most modern cargo ships, which are container ships and whose cargo is on- and off-loaded by dedicated cranes on the quay.

Typically, there are three major types of ships which are RO/RO capable. The first is automobile ferries, whose entire job is to quickly load, move and unload rolling vehicles. The second is automobile carriers - large cargo ships optimized for transporting cars (without their passengers) across oceans. The third is military sealift and PREPO ships. These latter are unique in that their cargoes are usually varied, and include vehicles of all sorts for both combat and logistics use. Although most such ships do require a port infrastructure to operate, at the extreme end are military landing ships which are designed to transport combat vehicles onto an unprepared beach.

Before RO/RO, all ships were loaded using cranes. RO/RO only really became important in the twentieth century as motorized transport came into its own, and not only the cargo but the vehicles themselves became items that were moved between shores.

DonJaime points out that after a particularly nasty disaster involving a capsizing car ferry, the term 'RORORO' came into sarcastic use - Roll On, Roll Off, Roll Over. Professor Pi surmises that this refers to the Herald of Free Enterprise capsizing and sinking.

This writeup is dedicated to leuryaks.

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