A train ferry is a ship designed to carry railway vehicles. Typically, one level of the ship is fitted with railway tracks, and the ship has a door at the front and/or rear to give access to the wharves. The wharf (sometimes called a "slip") has a ramp or linkspan that connects the railway proper to the ship, allowing for the water level to rise and fall with the tides. For an example of a specialized slip to receive railcars see ferry slip.
While railway vehicles can and are shipped on the decks or in the holds of ordinary ships, purpose-built train ferries are much quicker to load and unload, especially as several vehicles can be loaded or unloaded at once.
The first was built in 1849 by Thomas Bouch, engineer of the Edinburgh and Northern Railway, Scotland, to cross the Forth estuary between Granton and Burntisland. It was intended as a temporary measure until the railway could build a bridge, but this was not opened until 1890, its construction delayed in part by repercussions from the catastrophic failure of Bouch's Tay Rail Bridge.
The Norwegian train ferry Skagerak sank in September 7, 1966 on a journey between Kristiansand (Norway) and Hirtshals (Denmark) in heavy weather (Gale force winds) when the rear sea-gate was destroyed by heavy seas. Fortunately there was no loss of lives (although one person died afterwards). 6 freight cars went to bottom with the ship as well as some automobiles. The ferry was built in 1965.
A similar incident happened when the Canadian train ferry Patrick Morris sank on April 19, 1970 while assisting in a search and rescue operation for a sinking fishing trawler off the northeast coast of Cape Breton Island. The ferry was trying to maintain position to retrieve a body when her stern gates were overpowered by 30-foot waves; she sank within 30 minutes taking several rail cars and 4 crew members to the bottom of the Cabot Strait. There were 47 survivors.
Train ferries rarely sank because of sea-hazards, although they have some weaknesses linked to the very nature of transporting trains "on rail" on a ship.
These weaknesses include:
Trains are loaded at a rather high level, making the ship top-heavy.
The train deck is difficult to compartmentalise, so that sloshing flood water can destabilise the ship.
The sea doors where the trains go in and out are a weakness, even if placed at the rear of the ship.
The train carriages need to be strongly secured lest they break away and roll around.
A number of railroad carferries, such as the *SS Milwaukee, have been lost on the Great Lakes. These losses, though causes remain unconfirmed, were attributed to seas boarding the unprotected stern of the ship and swamping it in a severe storm. As a result, seagates were required on all new ships and required to be retrofitted on older vessels. In addition, two wooden crosslake railroad ferries were burned.