Main Physical Characteristics of ISO Containers

Main Physical Characteristics of ISO Containers

Source: adapted from Container Alliance.

The container changed the face of globalization, with the box recognized as the “humble hero” and one of the most influential inventions of the twentieth century. The principles behind containerization are simple. Transporting cargo into boxes or bags to shift it around more efficiently as a unit has always been seen as advisable. However, shipping containers were only made possible following the standardization of the dimensions of the different types of containers used in the mid-1960s. Created in 1961, the ISO technical committee on Freight containers (ISO/TC 104) has standardized almost every aspect of containers from their overall dimensions to how they can be stacked, to the twistlocks that securely fasten them to ship decks or truck chassis, to the terminology used to describe them.

The standard 20-foot container is the most commonly used box for the shipment of goods in ocean freight along with the 40-foot container. The dimensions are usually measured using the imperial system (feet) and specify both the exterior and interior (usable) dimensions. The standardization of cargo containers ensures containers can be stacked most efficiently, literally one on top of another. Although freight containers are manufactured worldwide, they are built to specific ISO specifications to allow for interoperability across intermodal transportation systems.

Many shippers prefer to use the largest load unit possible (e.g. 40-foot high cube containers) because it conveys economies of scale. However, weight restrictions can make the 20 foot a desirable option, particularly for transporting commodities. For instance, the weight restrictions on both the regular and the high cube forty footers are at around 30 short tons (or 28 metric tons), virtually the same as a 20 footer, so there are no gains in using a high cube container for heavy goods. Payload weight gets even smaller with 45 and 48-foot containers, underlining their specific role in transporting bulky but comparatively light goods. The majority of containers are made with weathering steel (Corten steel), which prevents rusting. They are water-resistant, protecting their contents from water intrusions.

Standardization enabled the expansion of the containerized seagoing transportation of goods. The usage of standardized containers resulted in a vast reduction in shipping costs. It allowed many countries that were previously isolated from global trade to put their products on the world market and consume imported goods.