2. Methodology
2.1. Classification scheme for liner shipping network perturbations
We define “network perturbation” as any change, positive or negative, to the existing state of main components of liner shipping networks. These include ports (nodes), routes operated by container liner services (links), vessels size (capacity), and transport demands (origin-destination pairs). Whether a perturbation is positive or negative often depends on the point of view of each stake holder. For example, the 1995 Port of Kobe disruption caused by an earthquake diverted local cargo to the ports of Osaka, Nagoya and Yokohama and transhipment cargo to the ports of Busan and Kaohsiung improving their cargo volumes and business. Though the port of Kobe recovered and the local cargo returned, significant transhipment volumes never returned (Lam, 2012). Positive or negative perturbations impacts are not isolated to port disruptions. For example, the improvement of existing infrastructure such as the Panama Canal expansion scheduled for completion in 2016 will relax vessel deployment upper bound constraints through this waterway. Potential impacts include transshipment cargo shifting in the Caribbean area from ports without capacity to receive post-panamax vessels to those with adequate infrastructure to accommodate such vessels (Rodrigue and Ashar, 2015).
In order to identify in which scenarios a container routing model can provide a contribution to the analysis of network perturbations, we proposed a classification scheme which differentiates between systemic and external perturbations. This differentiation allows to identify sources of disruptions which, from a modelling stand-point, dictate the main parameters of the network that will be modified.