Types of Container Ships

The container ship is the heart of intermodal transportation: a ship that--rather than carrying loose cargo, like boxes or crates stored in the ship's hold--carries truck-size containers, highway trailers or even truck-size containers within larger containers that are actually barges, on their deck and in their holds. These different freight configurations provide shippers with the flexibility offered by rail and highway, together with the savings afforded by sea transportation, the most cost-effective means of transportation.

History

After World War II, there was a surplus of Kaiser-built Liberty Ships; many of these vessels were mothballed by the U.S. Maritime Administration (MARAD) for storage at its James River, Virginia, National Defense Reserve Fleet facility, but some of the T-2 class tankers were adapted to carry highway trailers in coastal service. The first true container ships, those built specifically to carry highway trailers, appeared in 1951. The first American container ship, the Ideal X, was a former T-2 class tanker that was rebuilt for coastal service. It operated between ports on the East Coast and Gulf Coast of the United States for a company that would become Sea-Land Service.

Size

Container ships are measured in Twenty-foot Equivalent Units, or TEUs, based on the number of standard 20-foot highway containers they can carry. These standard "boxes" are 20 feet long, 8 feet wide and 8 1/2 feet high. The Ideal X could carry about 80 of the 35-foot-long highway trailers provided by its owner, equivalent to about 120 of today's 20-foot units. Today's largest container ship, The Emma Maersk, has a capacity of 15,200 TEU.

Significance

Transportation by sea has always been more economical than transportation by land. In ancient Egypt, goods were consolidated at ports and packed into baskets for shipping, a less costly and more timely way of moving goods than by a long caravan trip. When the Persian empire attacked the Greeks at Thermopylae, their logistical support was by ship. Shipwrecks dating back 2,000 years litter the shores of the Mediterranean and Black seas, a testimony to the effectiveness of low-cost seaborne freight compared to land routes and the uncertainties of borders, thieves and time lost in taking the longer routes. Container ships combine the benefits of freight consolidation and sea transportation with the benefits of direct access to multiple modes of transportation by eliminating the hassle and costs incurred with the repackaging of individual items as the mode of transportation changes.

Types of Container Ships and a National Defense Priority

There are three common types of container ship. First is the "box ship," loaded by specialized cranes with the familiar 20-foot and 40-foot highway containers that will be loaded onto a frame with truck wheels for movement to a destination. Next is the Roll On/Roll Off ship, known as RORO, where full tractor-trailers, trucks, tanks or other vehicles--with or without cargo--can be driven aboard, then driven off. Last is the Lift On/Lift Off ship, called LOLO where the highway containers are first parked inside a barge box--a box-shaped barge--then floated out to the waiting LOLO, where the ships on specialized cranes lift the barge aboard. All of these types of container ships have supported the U. S. Military in most actions since the end of the Vietnam War, including Desert Storm and the war against terrorism. The U. S. Maritime Administrator, Captain William Schubert, described the ships that complete the 12,000-mile trip to deliver essential supplies and equipment to American troops as a "steel bridge of democracy."

Potential

As shipping modalities change and as countries move to the fore in developing new modalities and shipping requirements, the design of container ships will likely change. Currently, there are plans for container ships that will carry more than 20,000 TEU. Their potential is only limited by the imagination of the naval architects and engineers who will bring them to life.

Resources

• Maersk Lines