Ro-pax

Roll-on/roll-off (RORO or ro-ro) ships are vessels designed to carry wheeled cargo, such as cars, trucks, semi-trailer trucks, trailers, and railroad cars, that are driven on and off the ship on their own wheels or using a platform vehicle, such as a self-propelled modular transporter. This is in contrast to lift-on/lift-off (LoLo) vessels, which use a crane to load and unload cargo.

RORO vessels have either built-in or shore-based ramps that allow the cargo to be efficiently rolled on and off the vessel when in port. While smaller ferries that operate across rivers and other short distances often have built-in ramps, the term RORO is generally reserved for large oceangoing vessels. The ramps and doors may be located in stern, bow or sides, or any combination thereof.

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.

The first modern train ferry was Leviathan, 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 was not yet capable enough to provide adequate support for the crossing over the Firth of Forth, which was roughly five miles across, a different solution had to be found, primarily for the transport of goods, where efficiency was key.

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Wikipedia