Gennaro Improta

An efficient transformation of the generalized vehicle routing problem

Abstract The Generalized Vehicle Routing Problem (GVRP) is the problem of designing optimal delivery or collection routes, subject to capacity restrictions, from a given depot to a number of predefined, mutually exclusive and exhaustive clusters. In this paper we describe an efficient transformation of the GVRP into a Capacitated Arc Routing Problem (CARP) for which an exact algorithm and several approximate procedures are reported in literature. It constitutes the only known approach for solving the GVRP.

The Capacitated Arc Routing Problem with intermediate facilities

This article introduces the Capacitated Arc Routing with Intermediate Facilities (CARPIF), a variant of the classical Capacitated Arc Routing Problem (CARP) in which the vehicle may unload or replenish at intermediate facilities. Two lower bounds are developed for the CARPIF: The first is based on the Rural Postman Problem (RPP) and the second one uses a relaxation of an integer linear formulation of the problem. Two upper bounds are also developed, based on the solution of an RPP and of a CARP. Computational results on a set of benchmark instances confirm the quality of the proposed bounds.

A multi-modal approach to the location of a rapid transit line

Abstract The location of a rapid transit line (RTL) represents a very complex decision problem because of the large number of decision makers, unquantifiable criteria and uncertain data. In this context Operational Research can help in the design process by providing tools to generate and assess alternative solutions. For this purpose two bicriterion mathematical programming models — the Maximum Coverage Shortest Path model and the Median Shortest Path model — have been developed in the past. In this paper a new bicriterion model, which can evaluate in a more realistic way the attractivity of an RTL is introduced. To calculate an estimation of the non-inferior solution set of the problem, a procedure based on a k -shortest path algorithm was developed. This approach was applied to a well-known sample problem and the results are discussed and compared with those obtained using a Median Shortest Path model.

An algorithm for the hierarchical Chinese postman problem

The Hierarchical Chinese Postman Problem (HCPP) is a variant of the classical Chinese Postman Problem, in which the arcs are partitioned into clusters and a precedence relation is defined on clusters. Practical applications of the HCPP include snow and ice control on the roads and determination of optimal torch paths in flame cutting. The HCPP is NP-hard in general, but polynomial-time solvable if the precedence relation is linear and each cluster is connected. For this case an exact algorithm, requiring a lower computational effort than previous procedures, is described.

The Arc Routing and Scheduling Problem with Transshipment

This article introduces theArc Routing and Scheduling Problem with Transshipment (ARPT), a particularArc Routing Problem whose applications arise in garbage collection. In the ARPT,the demand is collected by specially equipped vehicles, taken to a transfer station, shredded or compacted and, finally, transported to a dump site by means of high-capacity trucks. A lower bound, based on a relaxation of an integer linear formulation of the problem, is developed for the ARPT. A tailored Tabu Search heuristic is also devised. Computational results on a set of benchmark instances are reported.

Using gravity models for the evaluation of new university site locations: A case study

A fundamental aspect of competitive spatial models is the choice behaviour of potential customers to patronize a facility. Most of the models used to describe this phenomenon are essentially based on the adaptation of Newtons law of gravitation to the economic case (gravity model). This paper shows an application of this model to describe the behaviour of potential students in the choice of a university site. The results provided by the model have been compared with the actual data and show that the gravity model can describe the behaviour of potential students with good approximation.

Dynamic positioning of idle automated guided vehicles

An automated guided vehicle (AGV) is a mobile robot commonly used to carry loads in material handling systems (MHS). Once a transfer is completed, an AGV stops at a home position, a point where it can park until it is assigned a new task. Determining the home positions is an important control problem with a direct influence on the overall performance of the MHS. The problem can be viewed as a location-allocation problem on a network. In this paper two fast and effective heuristics which dynamically determine the home positions are proposed. The methods were tested using two real-world instances. The obtained results are shown and discussed.

Models for the schedule optimization problem at a public transit terminal

This work deals with the proposal of some models for the schedule optimization problem for public transit networks. In particular, we consider the case of a transit terminal where passengers are supposed to split among different lines of a service, or even change mode of transportation in case of intermodal systems. Starting from a given schedule for the transit lines arriving at the terminal, the aim is to decide the optimal schedule for the output lines, in such a way to balance the operative costs of the service and the passenger waiting time at the transit terminal. We propose two different models for this problem, which present strong similarities with some well known combinatorial optimization models. Computational results are also presented, showing the suitability of the models to solve real case studies.

The laser-plotter beam routing problem

Laser-plotters are used in the manufacturing industry to draw trademarks and decorations on the metallic surfaces of some products and devices. Given a pattern, the laser-plotter beam routing problem amounts to routing a laser-plotter beam in such a way that the total drawing time is minimised and some additional requirements are met. The aim of this paper is to model and solve the laser-plotter beam routing problem as a constrained Arc Routing Problem. Computational results on test problems with up to 225 vertices are reported.

Routing problems: a historical perspective

This paper presents an historical perspective on routing problems. Today a well-established class of optimization problems, routing problems have played a pivotal role in the development of Logistics as a discipline, even influencing other sectors not directly connected to management studies. The aim of this paper is to provide an overview of the evolution of this topic, starting from seminal contributions by Euler and Hamilton, and illustrating the most recent applications. This article is based on a longer article originally published in Italian (Bruno et al. 2010).