Source: Ashar and Rodrigue, 2012. All dimensions are in meters. LOA: Length overall. The loads displayed on deck represent maximal possible loads, which would involve a large share of empty containers. Containerships usually carry less containers because of weight restrictions and lack of demand.
- A) Early containerships. The first generation of containerships was composed of modified bulk vessels or tankers that could transport up 1,000 TEUs. The first containership, the "Ideal-X" was a converted World War II T2 tanker. The container was at the beginning of the 1960s an untested transport technology and reconverting existing ships proved out to be of lower costs and less risky. These ships were carrying onboard cranes since most port terminals were not equipped to handle containers. They were also relatively slow, with speeds of about 18 to 20 knots and could only carry containers on the converted decks and not in their bellyhold. Once the container began to be massively adopted at the beginning of the 1970s, the construction of the first fully cellular containerships (FCC; second generation) entirely dedicated for handling containers started. All containerships are composed of cells lodging containers in stacks of different height depending on the ship capacity. Cellular containership also offer the advantage of using the whole ship to stack containers, including below deck. Usually an extra of two containers in width can be carried above deck than below deck. Cranes were removed from the ship design so that more containers could be carried (cranes remain today on some specialized containerships). The ability of ports to handle cellular containerships ceased to be a major concern with the setting of specialized container terminals around the world. Cellular containerships were also much faster with speeds of 20-24 knots, which would become the speed of reference in containerized shipping.
- B) Panamax. During the 1980s economies of scale rapidly pushed for the construction of larger containerships; the larger the number of containers being carried the lower the costs per TEU. The process became a virtuous circle compounding larger volumes and lower costs, which significantly helped the diffusion of the container. The size limit of the Panama Canal, which came to be known as the panamax standard, was achieved in 1985 with a capacity of about 4,000 TEUs. Once this limit was achieved, a decade passed before a new generation of larger containerships was designed. At the same time panamax container ship designs were evolving to take maximum advantage of the canal's limitation in beam (Panamax Max). The original dimensions of the Panama Canal, built by the US Army Corps of Engineers, are similar to the dimensions of the US Inland Waterways locks, resulting in a narrow and long ship design.
- C) Post Panamax I and II. Going beyond panamax was perceived as a risk in terms of the configuration of shipping networks, additional handling infrastructure as well as draft limitations at ports. The APL C10 containership class, with a capacity of 4,500 TEUs, was introduced in 1988 and was the first containership class to exceeded the 32.2 m width limit of the Panama Canal. By 1996, full fledged Post Panamax containerships were introduced with capacities reaching 6,600 TEUs. The first Post Panamax ship classes where not much longer than the Panamax class, but wider. A ship above the panamax size requires a substantial amount of cargo to be used profitably along a service loop and by the late 1990s the rapid growth of global trade made such a ship class a marketable proposition. Once the panamax threshold was breached, ship size quickly increased with capacities reaching 8,000 TEUs (Post Panamax II; "Sovereign Class"). Post Panamax containerships triggered an infrastructure challenge for many ports since they require deeper drafts (at least 43 feet of draft) and highly efficient, but costly, portainers. Draft constraints became a factor placing pressures on ports to dredge to accommodate post panamax containerships.
- D) New-Panamax, or Neo-Panamax (NPX). Refers to ships designed to fit exactly in the locks of the expanded Panama Canal, which opened in June 2016. These ships have a capacity of about 12,500 TEU. Like its Panamax counterparts, New Panamax ships are likely to define a specific ship class able to service the Americas and the Caribbean, either from Europe or from Asia.
- E) Post Panamax III and Triple E. By 2006, a third generation of post panamax containerships came online when Maersk shipping line introduced a ship class having a capacity in the range of 11,000 to 14,500 TEUs; the Emma Maersk, (E Class). They were dubbed "Post New Panamax" since they are bigger than the specifications of the expanded Panama Canal. A further extension of the post panamax design led to the introduction of "Triple E" class ships of about 18,000 TEUs in 2013. It remains to be seen which routes and ports these ships would service, but they are limited mostly to routes between Asia and Europe. There are larger ship designs on the drawing boards, such as the "Malacca Max" class that could carry about 27,000-30,000 TEU, but they are not expected to be constructed within a decade.