1,720,993 research outputs found
The Multi-Trip Vehicle Routing Problem with Time Windows and Release Dates
No full textThe multi-trip vehicle routing problem with time windows and release dates is a variant of the multi-trip vehicle routing problem where a time window and a release date are associated with each customer. The release date represents the date when the merchandise requested by a customer becomes available at the depot. The interest for this problem comes from the field of city logistics and the study of delivery systems involving City Distribution Centers (CDC). In these systems, goods are first delivered to a CDC before being transferred to eco-friendly vehicles for final delivery. We propose to address the problem through a population-based algorithm, with a giant tour representation for individuals. An efficient labeling procedure allows turning giant tours into solutions. Experiments demonstrate the effectiveness of the method
Vehicle routing problems with multiple trips
No full textThis paper presents a survey on the multi-trip vehicle routing problem (MTVRP) and on related routing problems where vehicles are allowed to perform multiple trips. The first part of the paper focuses on the MTVRP. It gives an unified view on mathematical formulations and surveys exact and heuristic approaches. The paper continues with variants of the MTVRP and other families of routing problems where multiple trips are sometimes allowed. For the latter, it specially insists on the motivations for having multiple trips and the algorithmic consequences. The expected contribution of the survey is to give a comprehensive overview on a structural property of routing problems that has seen a strongly growing interest in the last few years and that has been investigated in very different areas of the routing literature
Two-echelon distribution with a single capacitated hub
No full textIn this paper, we investigate the synchronization between the two echelons in two-echelon urban distribution systems. The first echelon aims at transferring goods from a warehouse to a (single) city hub located in the city center. The second echelon, managed with a fleet of environmentally friendly vehicles, delivers goods to final customers, from the city hub. The two echelons are synchronized in time but also with regards to the capacity of the city hub. As far as we know, this is the first study considering the latter issue in the context of two-echelon distribution. To deal with the synchronization while optimizing the distribution, we propose a three-phase heuristic solution approach. At first, our approach optimizes the distribution for the second echelon. Then, it manages the synchronization. Finally, it optimizes the distribution for the first echelon. Population-based metaheuristics and integer programs are used. Results show the effectiveness of the method and permit to derive managerial insights on the distribution
The Capacitated Team Orienteering and Profitable Tour Problems
No full textTechnical Report n. 285, Department of Quantitative Methods, University of Bresci
Complexity of the VPR and SDVRP
No full textTechnical Report n. 331, Department of Quantitative Methods, University of Bresci
Simulation of Mutualized Urban Logistics Systems with Real-time Management
No full textThis work aims at proposing a new organization of urban merchandize distribution based on mutualized and optimized resources. In this context, our contribution is twofold. On one hand, we develop a set of models to manage merchandize distribution. We develop a new reservation system that enables customers to request a merchandize transportation service (delivery and collect) or to book a vehicle for self-service purposes. Requests are processed by two main decision modules (1) an online module that immediately searches for a feasible solution for a request, and decides to accept or reject it, and (2) an offline module that looks for optimized solutions starting from the feasible schedule defined by the online module. On the other hand, we develop a new discrete event simulator, called MODUMS which integrates the proposed models, implements such a logistic system and evaluates its economic and environmental impact. MODUMS takes as inputs realistic information about the transportation means, geographic data and demand information requests that are generated according to some probability distributions. It gives as outputs indicators on the impact of mutualization on the quality of urban logistics in terms of, for example, number of delayed or rejected requests, filling rate of vehicles, total distance and quantity of CO2
A heuristic branch-cut-and-price algorithm for the ROADEF/EURO challenge on Inventory Routing
No full textThis paper is part of the special section devoted to the ROADEF/EURO challenge on inventory routing. We propose an extended formulation that we address with a heuristic branch-cut-and-price method. Among the difficulties that we had to face are a fractional objective function, the simultaneous generation of constraints and columns, and a complex pricing problem. We evaluate our approach on the benchmark instances proposed for the challenge
Vehicle routing problems for city logistics
No full textThis paper surveys the vehicle routing problems met in cities for good distribution. It applies the following methodology. First, it gives an overview of the literature devoted to vehicle route optimization in cities. Then, it classifies and analyses urban logistic flows. As a result, it identifies the principal scientific challenges that need to be addressed: time-dependency, multi-level and multi-trip organization of the distribution, dynamic information. Finally, it focuses on each one of these challenges, analyses the main difficulties they imply and how they are treated in the literature
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