André Langevin

Continuous approximation models in freight distribution: An overview

This paper presents an overview of continuous approximation models that have been developed for freight distribution problems. A taxonomy of six classes is used to differentiate the problems and a brief review of each paper is provided. The paper stresses important principles and key results from the models and highlights gaps in the literature and areas for future work.

Integrated production and material handling scheduling using mathematical programming and constraint programming

In this article, we propose an integrated formulation of the combined production and material handling scheduling problems. Traditionally, scheduling problems consider the production machines as the only constraining resource. This is however no longer true as material handling vehicles are becoming more and more valuable resources requiring important investments. Their operations should be optimized and above all synchronized with machine operations. In the problem addressed in this paper, a job shop context is considered. Machines and vehicles are both considered as constraining resources. The integrated scheduling problem is formulated as a mathematical programming model and as a constraint programming model which are compared for optimally solving a series of test problems. A commercial software (ILOG OPLStudio) was used for modeling and testing both models.

A two-commodity flow formulation for the traveling salesman and the makespan problems with time windows

This paper presents a new two-commodity flow formulation for the traveling salesman problem. Each commodity corresponds to a resource that is either distributed or picked-up along the tour of all nodes. This formulation is particularly well-suited to handle time window constraints; the resource used is then the time. This formulation can be extended to the makespan problem. For a n-node proble, the linear relaxation of the formulation involves only O(n) constraints and O(n2) variables. Implementation issuesare discussed and numerical experimentations have been realized for problems of up to 40 nodes. (A)

A survey of models and algorithms for winter road maintenance. Part IV: Vehicle routing and fleet sizing for plowing and snow disposal

This is the last part of a four-part survey of optimization models and solution algorithms for winter road maintenance planning. The two first parts of the survey address system design problems for winter road maintenance. The third part concentrates mainly on vehicle routing problems for spreading operations. The aim of this paper is to provide a comprehensive survey of optimization models and solution methodologies for the routing of vehicles for plowing and snow disposal operations. We also review models for the fleet sizing and fleet replacement problems.

A survey of models and algorithms for winter road maintenance. Part III: Vehicle routing and depot location for spreading

Winter road maintenance planning involves a variety of decision-making problems related to the routing of vehicles for spreading chemicals and abrasives, for plowing roadways and sidewalks, for loading snow into trucks, and for transporting snow to disposal sites. These problems are very difficult and site specific because of the diversity of operating conditions influencing the conduct of winter road maintenance operations and the wide variety of operational constraints. As the third of a four-part survey, this paper reviews optimization models and solution algorithms for the routing of vehicles for spreading operations. We also review models for the location of vehicle and materials depots and for the assignment of crews to vehicle depots. The two first parts of the survey address system design problems for winter road maintenance. The fourth part of the survey covers vehicle routing problems for plowing and snow disposal operations.

A survey of models and algorithms for winter road maintenance: part I: system design for spreading and plowing

Winter road maintenance operations involve a host of decision-making problems at the strategic, tactical, operational, and real-time levels. Those operations include spreading of chemicals and abrasives, snow plowing, loading snow into trucks, and hauling snow to disposal sites. As the first of a four-part survey, this paper reviews optimization models and solution algorithms for the design of winter road maintenance systems for spreading and plowing operations. System design problems for snow disposal operations are discussed in the second paper. The two last parts of the survey mainly address vehicle routing, depot location, and fleet sizing models for winter road maintenance. The present paper surveys research on determining the level of service policy and partitioning a region or road network into sectors for spreading and plowing operations. We also describe the applied setting in which these problems arise.

Integrated scheduling of crane handling and truck transportation in a maritime container terminal

This paper studies the interactions between crane handling and truck transportation in a maritime container terminal by addressing them simultaneously. Yard trucks are shared among different ships, which helps to reduce empty truck trips in the terminal area. The problem is formulated as a constraint programming model and a three-stage algorithm is developed. At the first stage, crane schedules are generated by a heuristic method. At the second stage, the multiple-truck routing problem is solved based on the precedence relations of the transportation tasks derived from the first stage. At the last stage a complete solution is constructed by using a disjunctive graph. The three procedures are linked by an iterative structure, which facilitates the search for a good solution. The computational results indicate that the three-stage algorithm is effective for finding high-quality solutions and can efficiently solve large problems.

Synchronized arc routing for snow plowing operations

This paper introduces a synchronized arc routing problem for snow plowing operations. In this problem, routes must be designed in such a way that street segments with two or more lanes in the same direction are plowed simultaneously by different synchronized vehicles. A mixed integer formulation and an adaptive large neighborhood search heuristic are proposed. The performance of the proposed algorithm is evaluated over a large instance set, including artificial and real data. Computational results confirm the efficiency of the algorithm.

Dispatching, routing, and scheduling of two automated guided vehicles in a flexible manufacturing system

This article presents a new approach for planning the dispatching, conflict-free routing, and scheduling of automated guided vehicles in a flexible manufacturing system. The problem is solved optimally in an integrated manner, contrary to the traditional approach in which the problem is decomposed in three steps that are solved sequentially. The algorithm is based on dynamic programming and is solved on a rolling time horizon. Three dominance criteria are used to limit the size of the state space. The method finds the transportation plan minimizing the makespan (the completion time for all the tasks). Various results are discussed. A heuristic version of the algorithm is also proposed for an extension of the method to many vehicles.

A survey of models and algorithms for winter road maintenance. Part II: system design for snow disposal

This is the second part of a four-part survey of optimization models and solution algorithms for winter road maintenance planning. The first part addresses system design problems for spreading and plowing operations. The aim of this paper is to provide a comprehensive survey of optimization models and solution methodologies for the design of systems for snow disposal operations. These problems include partitioning a region or road network into sectors, locating snow disposal sites, allocating sectors to snow disposal sites, and allocating sectors to private companies or governmental agencies. The two last parts of the survey mainly concentrate on vehicle routing for winter road maintenance.