VRPTW

We consider a simulated annealing approach with a network reduction technique to solve a special case of a vehicle routing problem with time windows where routes have limited duration (VRPTW-LD). The objective is twofold: minimizing the travel time and the total number of vehicles required. The time-window constraint ensures delivery without delay, thus high level of customer satisfaction. The implementation of this algorithm for solving large-scale VRPTW-LD problems has positively impacted GE Appliances & Lighting's operation in terms of customer's satisfaction by reducing delivery time from three to two days, a 33% improvement, and by reducing the number of required trucks by half in some instances.

Citación: Rocha, L.; González, C. y Orjuela, J. (2011). Una revisión al estado del arte del problema de ruteo de vehículos: Evolución histórica y métodos de solución. Resumen Este artículo presenta una revisión bibliográfica acerca de la histo-ria, tipologías y métodos de solución del Problema de Ruteo de Vehículos (VRP). Explica las diferentes variaciones que han surgido, y hace referencia a las categorías básicas de VRP, los métodos de solución propuestos, así como sus tendencias. Palabras clave: Problema de Ruteo de Vehículos, Múltiples Via-jes, Métodos Exactos, Heurísticas, Metaheurísticas. Abstract This paper is a literature review of the history, categories, and solution methods of the vehicle routing problem with multiple trips (Multi-trip VRP). It explains the beginning of the concept of VRP and discusses the different variations that have arisen recently. Solution methods, approaches and tendencies to these variations are described with references to further studies. En el ámbito de competencia que caracteriza al siglo XXI, la logís-tica industrial es usada por las compañías con el fin de generar ventajas competitivas. Dentro de este contexto es de vital importancia los procesos de aprovisionamiento y/o distribución, por lo que el esta-blecimiento de las rutas para vehículos de la manera más óptima ha generado un gran interés investigativo. Como resultado se han pro-puesto un sin número de modelos que abarcan este problema con el fin de mejorar el desempeño logístico. El presente artículo se enfoca precisamente en este aspecto. En él se realiza una revisión del estado del arte acerca de la evolución del Problema de Ruteo de Vehículos (VRP, por sus siglas en inglés, Vehicle Routing Problem) desde su concepción. Se presenta una reseña

—This paper addresses the Vehicle Routing Problem (VRP) of a Home Health Care (HCC) service provider that serves patients requesting different types of care. In this problem, HCC services are provided by two types of personnel, nurses and health care aides, and the number of each type of personnel is limited. Each patient must be visited exactly once even if her servicing requires both personnel and is associated with a strict time window during which the service must be provided. We first present the 0-1 mixed integer programming formulation of the problem. Since the arising VRP is NP-hard, we then develop a Variable Neighborhood Search (VNS) algorithm to solve it. Next, we randomly generate a set of small-sized instances based on Solomon's benchmark problems for the VRP with Time-Windows and solve them using IBM ILOG CPLEX. To test the effectiveness of the VNS algorithm, we compare these solutions to those achieved by VNS. Our preliminary experiments show that VNS is able to find good results fast, yet the HCC crew constraints may complicate the problem. Keywords—Home care; health care; vehicle routing problem with time windows; variable neighborhood search