Since the late 1950s the ocean cargo container has revolutionized the seaborne and inland transport of general cargo throughout the world. The specialized container ship is a key element in an intermodal system developed to efficiently transport standard sized ocean freight containers. Containers are transported within cargo holds outfitted with vertical cells and on deck utilizing specially designed securing equipment.

A container ship is designed for the requirements of the intended service, including required service speed, number of containers by size and type and projected cargo weights. Container capacity is maximized within the available volume of the ship. Features are provided to enhance port productivity by allowing for faster loading and discharge. If shore side cranes are not available in some ports of the intended service, the ship may be equipped with self-sustaining capability. While container features are important, competition necessitates that the ship is reliable, efficiently powered and constructed and operated economically.

A container transport system differs from a break bulk operation in that cargo stowage is accomplished at a container terminal or by the shipper at the point of origin. Unique features of container ships are inherently associated with maximizing cargo stowage and with the system required to safely stow and secure cargo containers.

Containers stowed below deck, and sometimes at locations above deck, are stacked one on top of another within vertical cell guides consisting of angles or fabricated tees. An important component of the cell guide system is the flared entry guide at the top of the cell angles, which assists the crane operator in lowering the containers into each cell or stack. A properly designed system will facilitate container stowage, speed up crane cycle times, and will minimize the potential for damage to the containers and the ship structure during loading operations.

Above the weather deck, containers are typically stowed in stacks with the long dimension oriented fore and aft and the stacks spaced about 20 to 20mm apart, athwartship. Container stacks may be secured to the weather deck structure using a variety of schemes. The most common method utilizes lashings to secure each stack independently. In some cases, deck stowed containers are secured in cell guides.

Elevated platforms or lashing bridges may be provided between bays of containers on deck to permit the stowage of an additional tier of containers or heavier containers in the upper tiers.

Container ship designs cover a broad spectrum of ship sizes and speed requirements, ranging from small feeder ships to 10.000 plus TEU line haul ships. Speed-power requirements for a particular container ship may be guided by an economic evaluation of the intended service and the projected container cargo volumes.

Most new buildings are single screw ships powered by a direct coupled, low speed, two-stroke diesel engine. In general, container ships tend to be fine in hull form and fast. For liner ship companies, speed selection may not be driven by the lowest freight rate, but rather by the fastest delivery time and other customer service considerations.

Timely delivery periods allow distributors and retailers to minimize inventory and warehousing requirements. The total transit may involve two ore more modes of transport with linked schedules and, therefore, maintaining a schedule is very important. As a result, a strong emphasis is placed on speed and speed make up capability that will allow the ship to maintain its schedule even in heavy weather or in light of other unforeseen delays.

New designs for line haule ships reflect significant increases in size and continuing effort to provide faster transits. Previous experience and design limitations with regard to the size of low speed diesel engines, after body hull lines, propeller design, and the amount of power that can be delivered through a single shaft and propeller are constantly being challenged and improved. New development continues with preliminary design work and research for 10.000 TEU and larger ships. While there are some twin screw container ships, current diesel engines are surpassing 100.000 hp, allowing even the largest ship to be single shaft.