Analysis and Optimization of Long-Haul Transportation Problems.

摘要

Transportation plays a major role in the global economy since it underlies all economic and social activities. However, the transportation sector in developed countries differs considerably from that of developing countries. In this thesis, we focus on long-haul freight transportation in North America and East Africa. We analyze transportation problems through two very different realities. Accordingly, this thesis is divided into two parts of two chapters each. The problems are treated through methodologies rooted in operations research and econometrics. Our analyses provide answers to questions falling within the area of operations management and public policies.;In the first part of this thesis, we present and solve a rich vehicle routing problem arising in the less-than-truckload transportation industry. This study is motivated by the case of Groupe Robert Inc., but our contribution remains of general applicability. The problem under study contains two dominant features: a routing component which consists in determining the sequence of customers visited by each vehicle, and a scheduling component which consists in planning the rest periods and the service time of each customer. The major contribution of the first chapter is the development and integration of different sophisticated scheduling algorithms, embedded within a tabu search heuristic tackling the vehicle routing component, defining truck driver schedules complying with the hour of service regulations in the United States. The results show that solutions can be greatly improved by integrating multiple possibilities for planning rest periods and the gains vary depending on the complexity of the implemented scheduling algorithm.;In the second part of this thesis, we address issues related to long-haul transportation in the context of food distribution in East Africa. Our study is motivated, on the one hand, by the case of the World Food Programme (WFP) in Ethiopia and, on the other hand, by all the different organizations involved in the supply chain at a regional level in Kenya. To transport food aid, the WFP primarily contracts with third-party transport carriers in markets that are not well understood. In the first chapter of this part, we propose a methodology based on econometric models in order to study the international and domestic Ethiopian transportation markets. We analyse historical contracts between WFP and private carriers using multiple linear regression to gain insights about these markets and to determine which factors better explain transportation tariffs. The results show that the major determinants of the truckload pricing structure are both the road conditions and the market structure. However, dominance and counterfactual analyses indicate that improving competition intensity has a greater impact on reducing transportation tariffs than improving the infrastructure, at least in the short-term. We also show how predictive models can be used to support the transportation procurement process and thus contribute to improve the shipper supply chain overall performance and refine budgeting for transportation operations.;In summary, we solve different applied problems related to long-haul transportation planning. These problems arise in organizations operating in economic contexts where the levels of maturity are clearly distinctive. Solution approaches used to address each problem are suitable for their particular contexts. Decision tools, such as the one we have developed in this thesis, can help decision makers handle simultaneously various features when planning transportation operations and establish a suitable solution. (Abstract shortened by UMI.).