large quantities of cars came into service in the early 1960s. These ships still had their own loading gear and so-called hanging decks inside. They were, for example, chartered by the German Volkswagen AG to transport vehicles to the U.S. and Canada. During the 1970s, the market for exporting and importing cars has increased dramatically and the number and type of ROROs has increased also. In 1970 Japan's K Line built the Toyota Maru No. 10, Japan's first pure car carrier, and in 1973 built the European Highway, the largest pure car carrier (PCC) at that time, which carried 4,200 automobiles. Today's pure car carriers and their close cousins, the pure car/truck carrier (PCTC), are distinctive ships with a box-like superstructure running the entire length and breadth of the hull, fully enclosing the cargo. They typically have a stern ramp and a side ramp for dual loading of thousands of vehicles (such as cars, trucks, heavy machineries, tracked units, Mafi roll trailers, and loose statics), and extensive automatic fire control systems. The PCTC has liftable decks to increase vertical clearance, as well as heavier decks for "high-and-heavy" cargo. A 6,500-unit car ship, with 12 decks, can have three decks which can take cargo up to with liftable panels to increase clearance from on some decks. Lifting decks to accommodate higher cargo reduces the total capacity. These vessels can achieve a cruising speed of at eco-speed, while at full speed can achieve more than . With the building of Wallenius Wilhelmsen Logistics's 8,000 car-equivalent unit (CEU) car carrier Faust out of Stockholm in June 2007, car carriers entered a new era of the large car and truck carrier (LCTC). Currently, the largest are Höegh Autoliners, six Horizon class vessels with capacity of 8,500 CEU each. The car carrier Auriga Leader, belonging to Nippon Yusen Kaisha, built in 2008 with a capacity of 6,200 cars, is the world's first partially solar powered ship. Seaworthiness The seagoing RORO car ferry, with large external doors close to the waterline and open vehicle decks with few internal bulkheads, has a reputation for being a high-risk design, to the point where the acronym is sometimes derisively expanded to "roll on/roll over". An improperly secured loading door can cause a ship to take on water and sink, as happened in 1987 with . Water sloshing on the vehicle deck can set up a free surface effect, making