A Branch-and-Cut Algorithm for the Capacitated Open Vehicle Routing Problem

In open vehicle routing problems, the vehicles are not required to return to the depot after completing service. In this paper, we present the first exact optimization algorithm for the open version of the well-known capacitated vehicle routing problem (CVRP). The algorithm is based on branch-and-cut. We show that, even though the open CVRP initially looks like a minor variation of the standard CVRP, the integer programming formulation and cutting planes need to be modified in subtle ways. Computational results are given for several standard test instances, which enables us for the first time to assess the quality of existing heuristic methods, and to compare the relative difficulty of open and closed versions of the same problem.Vehicle routing; branch-and-cut; separation

The Relationship between Vehicle Routing & Scheduling and Green Logistics - A Literature Survey

The basic Vehicle Routing and Scheduling Problem (VRSP) is described followed by an outline of solution approaches. Different variations of the basic VRSP are examined that involve the consideration of additional constraints or other changes in the structure of the appropriate model. An introduction is provided to Green Logistics issues that are relevant to vehicle routing and scheduling including discussion of the environmental objectives that should be considered. Particular consideration is given to VRSP models that relate to environmental issues including the timedependent VRSP, the transportation of hazardous materials and dynamic VRSP models. Finally some conclusions are drawn about further research needs in this area and the relation to road pricing

The potential use of e-procurement in the Malaysian palm oil industry supply chain

E-procurement is electronic methods of conducting business transactions particularly purchasing activities. Many companies around the world have started to apply the technologies though there are still some which refuse to utilize them. The objective of this paper was to investigate the application of e-procurement technologies in managing purchasing activities among the Malaysian Palm Oil Industry (MPOI) supply chain players. Responses from the representative player of each stage of the MPOI supply chain were gathered via in-depth interviews using an open ended questionnaire. A detailed analysis based on content analysis from the responses revealed that e-procurement technologies could be a potential tool to increase the efficiency of purchasing activities, enhance purchasing and searching processes, as well as providing relevant information on materials, and aid in the reduction of human error. Certain products for example fresh fruit bunch (FFB), crude palm oil (CPO), crude palm kernel oil (CPKO) and palm kernel however were found to be impractical to use e-procurement tools due to several reasons. These products were commonly supplied by very established suppliers who are quite conventional in their business. Thus e-procurement tools are not often used in their purchasing activities. This paper concluded that e-procurement technologies were not 'really' available in the MPOI supply chain

Disrupted Capacitated Vehicle Routing Problem with Order Release Delay

With the popularity of the just-in-time system, more and more companies are operating with little or no inventories, which make them highly vulnerable to delays on supply. This paper discusses a situation when the supply of the commodity does not arrive at the depot on time, so that not enough of the commodity is available to be loaded on all vehicles at the start of the delivery period. New routing plans need to be developed in such a case to reduce the impact the delay of supply may have on the distribution company. The resulting vehicle routing problem is different from other types of vehicle routing problems as it involves waiting and multiple trips. Two approaches have been developed to solve the order release delay problem, both of which involve a Tabu Search algorithm. Computational results show the proposed approaches can largely reduce the disruption costs that are caused by the delayed supply and they are especially effective when the length of delay is long

Combinatorial optimization and Green Logistics

International audienceThe purpose of this paper is to introduce the area of Green Logistics and to describe some of the problems that arise in this subject which can be formulated as combinatorial optimization problems. The paper particularly considers the topics of reverse logistics, waste management and vehicle routing and scheduling

Preface [Special Issue: International Symposium on Combinatorial Optimisation (CO2000)]

Preface [Special Issue containing a selection of papers presented at the International Symposium on Combinatorial Optimisation (CO2000) held at the University of Greenwich, London, from 12-14 July 2000