Intermodal container in the context of Twistlock

Maritime transport (or ocean transport) or more generally waterborne transport, is the transport of people (passengers) or goods (cargo) via waterways. Freight transport by watercraft has been widely used throughout recorded history, as it provides a higher-capacity mode of transportation for passengers and cargo than land transport, the latter typically being more costly per unit payload due to it being affected by terrain conditions and road/rail infrastructures. The advent of aviation during the 20th century has diminished the importance of sea travel for passengers, though it is still popular for short trips and pleasure cruises. Transport by watercraft is much cheaper than transport by aircraft or land vehicles (both road and rail), but is significantly slower for longer journeys and heavily dependent on adequate port facilities. Maritime transport accounts for roughly 80% of international trade, according to UNCTAD in 2020.

Maritime transport can be realized over any distance as long as there are connecting bodies of water that are navigable to boats, ships or barges such as oceans, lakes, rivers and canals. Shipping may be for commerce, recreation, or military purposes, and is an important aspect of logistics in human societies since early shipbuilding and river engineering were developed, leading to canal ages in various civilizations. While extensive inland shipping is less critical today, the major waterways of the world including many canals are still very important and are integral parts of worldwide economies. Particularly, especially any material can be moved by water; however, water transport becomes impractical when material delivery is time-critical such as various types of perishable produce. Still, water transport is highly cost effective with regular schedulable cargoes, such as trans-oceanic shipping of consumer products – and especially for heavy loads or bulk cargos, such as coal, coke, ores or grains. Arguably, the Industrial Revolution had its first impacts where cheap water transport by canal, navigations, or shipping by all types of watercraft on natural waterways supported cost-effective bulk transport.

A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping.Things kept inside of a container are protected on several sides by being inside of its structure. The term is most frequently applied to devices made from materials that are durable and are often partly or completely rigid.

A container can also be considered as a basic tool, consisting of any device creating a partially or fully enclosed space that can be used to contain, store, and transport objects or materials.

Containerization is a system of intermodal freight transport using intermodal containers (also called shipping containers, or ISO containers). Containerization, also referred as container stuffing or container loading, is the process of unitization of cargoes in exports. Containerization is the predominant form of unitization of export cargoes today, as opposed to other systems such as the barge system or palletization. The containers have standardized dimensions. They can be loaded and unloaded, stacked, transported efficiently over long distances, and transferred from one mode of transport to another—container ships, rail transport flatcars, and semi-trailer trucks—without being opened. The handling system is mechanized so that all handling is done with cranes and special forklift trucks. All containers are numbered and tracked using computerized systems.

Containerization originated several centuries ago but was not well developed or widely applied until after World War II, when it dramatically reduced the costs of transport, supported the post-war boom in international trade, and was a major element in globalization. Containerization eliminated manual sorting of most shipments and the need for dock front warehouses, while displacing many thousands of dock workers who formerly simply handled break bulk cargo. Containerization reduced congestion in ports, significantly shortened shipping time, and reduced losses from damage and theft.

The Port of Singapore is a collection of facilities and terminals that conduct maritime trade and handle Singapore's harbours and shipping. Since 2015, it has been ranked as the world's top maritime capital. Currently, it is ranked as the world's second-busiest port in terms of total shipping tonnage, while also transshipping a fifth of the world's shipping containers, and half of the world's annual crude oil supplies, alongside being ranked as the world's busiest transshipment port. Furthermore, it was also ranked as the world's busiest port in terms of total cargo tonnage handled until 2010, when it was surpassed by the Port of Shanghai.

Due to the city-state's strategic location, Singapore has served as a significant entrepôt and trading post on an international level for at least two centuries. During the contemporary era, its ports have been regarded not merely as an economic boon for the country, but as vitally important for the country's economic development since Singapore lacks land and natural resources. Additionally, the port is regarded as particularly important for importing natural resources, and then later re-exporting products after they have been domestically refined and shaped in some manner, for example, wafer fabrication or oil refining to generate value-added revenue. The Port of Singapore is also the world's largest bunkering port. Moreover, the majority of ships that pass between the Indian Ocean and the Pacific Ocean go through the Singapore Strait. The Straits of Johor on the country's north are impassable for ships due to the Johor-Singapore Causeway, built in 1923, which links the town of Woodlands, Singapore, to the city of Johor Bahru in Malaysia.

Transshipment, trans-shipment or transhipment is the shipment of goods or containers to an intermediate destination, then to another destination.

One possible reason for transshipment is to change the means of transport during the journey (e.g., from ship transport to road transport), known as transloading. Another reason is to combine small shipments into a large shipment (consolidation), or the opposite: dividing a large shipment into smaller shipments (deconsolidation). Transshipment usually takes place in transport hubs. Much international transshipment also takes place in designated customs areas, thus avoiding the need for customs checks or duties, otherwise a major hindrance for efficient transport.

Double-stack rail transport is a form of intermodal freight transport in which railroad cars carry two layers of intermodal containers. Invented in the United States in 1984, it is now being used for nearly 70% of United States intermodal shipments. Using double stack technology, a freight train of a given length can carry roughly twice as many containers, sharply reducing transport costs per container. On United States railroads, special well cars are used for double-stack shipment to reduce the needed vertical clearance and to lower the center of gravity of a loaded car. In addition, the well car design reduces damage in transit and provides greater cargo security by cradling the lower containers so their doors cannot be opened. A succession of larger container sizes have been introduced to further increase shipping productivity in the United States.

Double-stack rail operations are growing in other parts of the world, but are often constrained by clearance and other infrastructure limitations.

A well car, also known as a double-stack car (or also intermodal car/container car), is a type of railroad car specially designed to carry intermodal containers (shipping containers) used in intermodal freight transport. The "well" is a depressed section that sits close to the rails between the wheel trucks of the car, allowing a container to be carried lower than on a traditional flatcar. This makes it possible to carry a stack of two containers per unit on railway lines (double-stack rail transport) wherever the structure gauge assures sufficient clearance.

The top container is secured to the bottom container either by a bulkhead built into the car — possible when bottom and top containers are the same dimensions, or through the use of inter-box connectors (IBC). Four IBCs are needed per well car. In the terminal there are four steps: unlock and lift off the top containers of an inbound train, remove the bottom containers, insert outbound bottom containers, lock assembly after top containers emplaced. Generally this is done car-by-car unless multiple crane apparatus are employed.

A freight rate (historically and in ship chartering simply freight) is a price at which a certain cargo is delivered from one point to another. The price depends on the form of the cargo, the mode of transport (truck, ship, train, aircraft), the weight of the cargo, and the distance to the delivery destination. Many shipping services, especially air carriers, use dimensional weight for calculating the price, which takes into account both weight and volume of the cargo.

For example, bulk coal long-distance rates in America are approximately 1 cent/ton-mile. So a 100 car train, each carrying 100 tons, over a distance of 1000 miles, would cost $100,000. On the other hand, Intermodal container shipping rates depend heavily on the route taken over the weight of the cargo, just as long as the container weight does not exceed the maximum lading capacity. Prices can vary between $300-$10,000 per Twenty foot equivalent unit (TEU) depending on the supply and demand of a given route.

Rail freight transport is the use of railways and trains to transport cargo, as opposed to passengers.

A freight train, cargo train, or goods train is a group of freight cars (US) or goods wagons (International Union of Railways) hauled by one or more locomotives on a railway, transporting cargo all or some of the way between the shipper and the intended destination as part of the logistics chain. Trains may haul bulk material, intermodal containers, general freight or specialized freight in purpose-designed cars. Rail freight practices and economics vary by country and region.

Intermodal freight transport involves the transportation of freight in an intermodal container or vehicle, using multiple modes of transportation (e.g., rail, ship, aircraft, and truck), without any handling of the freight itself when changing modes. The method reduces cargo handling, and so improves security, reduces damage and loss, and allows freight to be transported faster. Reduced costs over road trucking is the key benefit for inter-continental use. This may be offset by reduced timings for road transport over shorter distances.

This article lists the world's busiest container ports (ports with container terminals that specialize in handling goods transported in intermodal shipping containers), by total number of twenty-foot equivalent units (TEUs) transported through the port. The table lists volume in thousands of TEU per year. The vast majority of containers moved by large, ocean-faring container ships are 20-foot (1 TEU) and 40-foot (2 TEU) ISO-standard shipping containers, with 40-foot units outnumbering 20-foot units to such an extent that the actual number of containers moved is between 55%–60% of the number of TEUs counted.

The latest ranking reflected the figures for the year 2025, as published in the Lloyds List Top 100 and World Shipping Council (2025 figures), unless otherwise indicated.

A container ship (also called boxship or spelled containership) is a cargo ship that carries all of its load in truck-size intermodal containers, in a technique called containerization. Container ships are a common means of commercial intermodal freight transport and now carry most seagoing non-bulk cargo.

Container ship capacity is measured in twenty-foot equivalent units (TEU). Typical loads are a mix of 20-foot (1-TEU) and 40-foot (2-TEU) ISO-standard containers, with the latter predominant.

The twenty-foot equivalent unit (abbreviated TEU or teu) is a general unit of cargo capacity, often used for container ships and container ports. It is based on the volume of a 20-foot-long (6.1 m) intermodal container, a standard-sized metal box that can be easily transferred between different modes of transportation, such as ships, trains, and trucks.

A flatcar (US) (also flat car, or flatbed) is a piece of rolling stock that consists of an open, flat deck mounted on trucks (US) or bogies (UK) at each end. Occasionally, flat cars designed to carry extra heavy or extra large loads are mounted on a pair (or rarely, more) of bogies under each end. The deck of the car can be wood or steel, and the sides of the deck can include pockets for stakes or tie-down points to secure loads. Flatcars designed for carrying machinery have sliding chain assemblies recessed in the deck.

Flatcars are used for loads that are too large or cumbersome to load in enclosed cars such as boxcars, but which will not be harmed by the weather. They are also often used to transport intermodal containers (shipping containers) or trailers as part of intermodal freight transport shipping.