S-class ferries (also known as the Spirit class or Super ferries) are roll-on/roll-off (RORO) ferries operated by BC Ferries in British Columbia, Canada. They are the largest ferries in the BC Ferries fleet. The class comprises two ships, and , which were completed in 1993 and 1994 respectively. They serve the ferry route between Tsawwassen and Swartz Bay. In 2017, the class underwent conversion to a dual-fuel propulsion system that would allow them to use either marine diesel fuel or liquefied natural gas. Design and description The S-class roll on/roll off ferries are the largest vessels in the BC Ferries fleet. They are long overall and between perpendiculars with a beam of . The vessels have a displacement of , an initial and . The gross tonnage later increased to 21,935 for Spirit of Vancouver and 21,958 for Spirit of British Columbia as of 2018. The vessels were initially powered by four MAN 6L40/54 diesel engines driving two shafts creating . The ferries have a maximum speed of . In 2018, the ferries began a mid-life refit that involved changing the propulsion system to a dual-fuel system comprising four Wärtsilä 34DF dual-fuel engines which allow the ships to use either marine diesel oil or liquefied natural gas to power the ship. Further changes include navigation and propulsion equipment, steering and evacuation systems, lighting and air conditioning. Passenger areas were upgraded including the lounges, bathrooms and retail areas. The ferries have capacity for 2,100 passengers and crew and 358 automobiles. The ferries are equipped with lounges and cafes. Ships in class History The two ferries, Spirit of British Columbia and Spirit of Vancouver Island, were constructed in two pieces. The ferries' foreparts were built by Allied Shipbuilders of North Vancouver, British Columbia. The rest of the ships was constructed by Integrated Ferry of Esquimalt, British Columbia. The two sections were joined and Spirit of British Columbia was completed in February 1993, with Spirit of Vancouver Island completed in February 1994. Spirit of British Columbia was assigned to the Tsawwassen–Swartz Bay route and Spirit of Vancouver Island to the inverse Swartz Bay–Tsawwassen route. On September 14, 2000, Spirit of Vancouver Island collided with the Star Ruby while attempting to overtake the vessel in a narrow channel. The accident report found that pleasure craft had ignored all warnings of the impending collision. Two passengers aboard Star Ruby later died as a result of