An ocean liner is usually a ship esigned to transport people from one seaport to another along regular long-distance maritime routes according to a schedule. Liners may also carry cargo, and may sometimes be used for other purposes (e.g. for pleasure cruises or as troopships). Cargo vessels running to a schedule are sometimes referred to as liners. The category does not include ferries or other vessels engaged in short-sea trading, nor dedicated cruise ships where the voyage itself, and not transportation, is the prime purpose of the trip. Nor does it include tramp steamers even if equipped to handle limited numbers of passengers, nor other cargo vessels (although many shipping companies refer to themselves as "lines" and their container ships, which often operate over set routes according to established schedules, as "liners"). Ocean liners typically were strongly built with high freeboards to withstand sea states and adverse conditions encountered in the open ocean, and had large capacities for fuel, victuals, and other stores which would be consumed on voyages which took from several days to several weeks.