Source: Adapted from J. Woxenius (2010) “Flexibility vs. Specialisation in European Short Sea Shipping”, International Association of Maritime Economists, Lisbon, Portugal.
A wide variety of ship designs are servicing the maritime transport market. Their flexibility can be characterized by their commercial and functional openness:
- Commercial openness. Defined as the range of customers accepted for a specific transport service. This can be an active decision by the transport service provider, a natural result of the fundamental design of the transport system, or dictated by regulation of the transport market. While a general ferry ship will accept almost any cargo that can be carried on the road, often on a first-come, first-serve basis, a crude tanker can only be chartered by large conglomerates directly involved in the oil commodity chain.
- Functional openness. Defined as the scope of cargoes or cargo containment technologies accepted by a transport system. This can also be an active choice or dictated by the pattern of transport demand or regulation. A system with a low functional openness is specially adapted to suit a certain cargo or type of unit load and severely restricts commercial openness. For instance, a general cargo ship can accommodate virtually any cargo type, which commonly changes for each chartered voyage. An LNG carrier is designed to carry solely liquid natural gas.
Each ship class also has size variations, often to take advantage of economies of scale if the demand is substantial enough. Containerships, bulk, and crude carriers are particularly suitable for an extensive range of size variations.