Ro-Ro

Ro-Ro, meaning roll-on/roll-off, is a method of ship design and cargo handling built around wheeled cargo that can be driven aboard under its own power or on trailers. Instead of lifting cargo through hatches with cranes, a Ro-Ro ship has ramps (usually at the stern, sometimes at the bow or side) that bridge to the shore so vehicles can be driven directly on and off. Inside, the ship is arranged as a series of vehicle decks connected by internal ramps, giving a large, continuous space that vehicles can move through. This makes loading and discharging very fast, which is why the method dominates vehicle and ferry trades.

Several ship types use the Ro-Ro principle. Pure Car and Truck Carriers, or PCTCs, are tall, boxy ships built to carry thousands of cars and other vehicles on many decks between manufacturing regions and markets. Ro-Ro ferries carry passengers together with cars, coaches and freight trailers on short sea and coastal routes. ConRo ships combine a Ro-Ro capability with container capacity, and Ro-Pax vessels blend substantial passenger accommodation with a freight and vehicle deck. Unaccompanied trailers and heavy project cargo on special roll-trailers are also handled this way.

Ro-Ro operations carry distinctive safety concerns that shape their design and regulation. The large open vehicle decks that make loading efficient can be dangerous if water enters them, because free water spreading across a wide deck can rapidly destroy a ship's stability — a lesson learned from several serious ferry disasters and reflected in strict rules on bow and stern door integrity and damage stability. Securing vehicles against movement in a seaway, controlling exhaust fumes and fire risk on the vehicle decks, and managing the rapid embarkation and disembarkation of passengers are all central to safe Ro-Ro operation.