Source: Adapted from J. Woxenius (2010) "Flexibility vs. Specialisation in European Short Sea Shipping", International Association of Maritime Economists, Lisbon, Portugal.
- 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. Also, this can be an active choice or can be 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 the commercial openness. For instance, a general cargo ship can accommodate virtually any cargo type, which commonly change for each chartered voyage, a LNG carrier is designed to carry solely liquid natural gas.