Models and algorithms for the empty container repositioning and its integration with routing problems

The introduction of containers has fostered intermodal freight transportation. A definition of intermodality was provided by the European Commission as " a characteristic of a transport system whereby at least two different modes are used in an integrated manner in order to complete a door-to-door transport sequence " EUROPA 2005. The intermodal container transportation leads to several benefits, such as higher productivity during handling phases and advantages in terms of security, losses and damages. However, the distribution of containers comes with a drawback: due to directional imbalances in freight flows, some areas tend to accumulate unnecessary empty containers, while others face container shortages. For example, in 2007 the Trans-Pacific trade container flow from Asia to North America was estimated at 14.5 million TEUs (Twenty foot Equivalent Unit), while the opposite direction only had 5.6 million TEUs " Review of maritime transport, United Nations, New York, 2008 ". As a consequence, carries were requested to reposition about 9 million TEUs from North America to Asia, in order to meet future transportation opportunities. Several planning models were developed for carriers in order to manage both loaded and empty containers profitably, Crainic 2003. However, they were built to operate under normal circumstances, neglecting the fact that networks are increasingly affected by both uncertainty and vulnerability, which may result in disruptions. These disruptions affect the normal operations of facilities, and make them partially or totally non-functional. Disruptions may be generated by unexpected events, due to both natural causes (hurricanes, earthquakes, etc.) and human-generated ones (accidents, failures, etc.). To make matters worse, widely adopted " just-in-time " supply chains make manufacturers vulnerable to disruptions if containers do not reach assembly plants in time. " The lack of key parts could reduce output, employment, and income for individual companies by amounts larger than the value of the delayed part and in areas and businesses far removed from the facility where a disruption occurred " Office 2006. Therefore, it is not enough for carriers to serve customers while operating at the lowest costs, because unexpected future evolutions cannot be ignored at all, even if they will not be observed. Proactive strategies should be adopted to become I Thesis introduction more resilient, i.e., deploying contingency plans for smoothly continuing operations whenever disruptions occur. Considering a hurricane for example, a forecast may preventively stop all activities of a port, but other forecasts may not exclude weather improvements which allow …