Efficient GRASP+VND and GRASP+VNS metaheuristics for the traveling repairman problem

The traveling repairman problem is a customer-centric routing problem, in which the total waiting time of the customers is minimized, rather than the total travel time of a vehicle. To date, research on this problem has focused on exact algorithms and approximation methods. This paper presents the first metaheuristic approach for the traveling repairman problem

Freight Distribution Problems in Congested Urban Areas: Fast and Effective Solution Procedures to Time-Dependent Vehicle Routing Problems

Congestion is a common phenomenon in all medium to large cities of the world. Reliability of freight movement in urban areas is an important issue to manufacturing or service companies whose operation is based in just-in-time approaches. These companies tend to provide high value or time sensitive products/services. As congestion increases, carriers face increasing challenges to satisfy their time sensitive customers in an economical way. Route designs or schedules which require long computation times or ignore travel time variations will result in inefficient and suboptimal solutions. Poorly designed routes that lead freight vehicles into congested arteries and streets not only increases supply chain and logistics costs but also exacerbate externalities associated with freight traffic in urban areas such as greenhouse gases, air pollution, noise, and accidents. Whilst it is rarely possible to entirely avoid the impacts of congestion, it is feasible to schedule operations so that the effects of congestion are minimized. Better scheduling can be effectively supported by the advent of inexpensive and ubiquitous Information and Communication Technologies (ICT). The use of mobile phone technology and on-board routing devices allows fluid communication between truck drivers and fleet operators in real-time. In such a real time operation it becomes possible to dynamically reassign vehicles, including modifying the order in which customers are served and diverting a vehicle already en-route to service another customer. However, without fast routing methods that can take advantage of real time congestion information carriers cannot reap the benefits of real-time information. From the operational point of view, congestion creates a substantial variation in travel times during peak morning and evening hours. This is problematic for all vehicle routing models which rely on a constant value to represent vehicle speeds. And while the ubiquitous availability of real time traffic information allows drivers to reactively alter routes and customer service sequences to better cope with congestion, static routing models are unable to take advantage of these advances in real-time information provision in order to proactively find adequate routing solutions. In addition, changes in travel time caused by congestion cannot be accurately represented in static models. Research in time-dependent vehicle routing problem is comparatively meager and current solution methods are inadequate for practical carrier operations which need to provide fast solutions for medium to large instances. Even faster solution methods are essential to take advantage of real time information. The major aim of this proposal is to develop and evaluate new methods for vehicle routing in congested urban areas. The emphasis will be placed on improving the running time of the existing methods

Resolución de un VRP con ventanas móviles mediante el uso del algoritmo Cuckoo Search

En este Trabajo Fin de Máster se trata de resolver un problema de rutado de vehículos destinado al ecommerce (EC-VRP) mediante un algoritmo bioinspirado, el algoritmo de la Búsqueda Cuco o Cuckoo Search (CS). El EC-VRP cuenta con las mismas características que el VRPTW (con ventanas temporales) tradicional, pero con la peculiaridad de que cada cliente cuenta con tres localicaziones distintas donde se les puede entregar la mercancía, teniendo que realizar la entrega en tan solo una de ellas. Además, estas localizaciones pueden contar con ventanas temporales disntintas.This work aims to solve a vehicle routing problem for e-commerce (EC-VRP) using a bioinspired algorithm, the Cuckoo Search (CS) algorithm. The EC-VRP has the same characteristics as the traditional VRPTW (with time window constraints), but with the peculiarity that each customer has three different locations where the goods can be delivered, having to make the delivery in only one of them. In addition, these locations have different time windows.Universidad de Sevilla. Máster en Ingeniería Industria

Travelling Salesman Problem Application in Particular Logistics Enterprise

Tato práce se zaobírá problematikou optimální distribuce. Čitatel se seznámí s problémy spojenými s distribucí. Kromě toho jsou v této práci vysvětleny problémy obchodního cestujícího, tzv. "vehicle routing problem" a jeho varianty. Dále je zde možné najít přehled přístupů k řešení "vehicle routing problem". V části zaměřené na problém z praxe se nachází analýza distribuce skutečné společnosti. V druhé polovině práce je představena aplikace, která by mohla snížit náklady na distribuci analyzované firmy. Testování je zaměřeno zejména na prozkoumání VRPCL (Vehicle Routing Problem with Continuos Loading), tedy problém plánovaní tras vozidel s průběžným nakládáním.This paper deals with optimal distribution issues. One may find listed problems of real life linked to distribution. Moreover, there are explained travelling salesman problem, vehicle routing problem and its variants. This work brings an overview of different ways how to solve vehicle routing problem. In practical part, there is an analysis of distribution of real company. The concept of application is presented in the second part of this paper. This concept could reduce costs of distribution in analyzed company. Testing is aimed mainly on the variant VRPCL (Vehicle Routing Problem with Continuos Loading).

OPTIMIZATION OF RAILWAY TRANSPORTATION HAZMATS AND REGULAR COMMODITIES

Transportation of dangerous goods has been receiving more attention in the realm of academic and scientific research during the last few decades as countries have been increasingly becoming industrialized throughout the world, thereby making Hazmats an integral part of our life style. However, the number of scholarly articles in this field is not as many as those of other areas in SCM. Considering the low-probability-and-high-consequence (LPHC) essence of transportation of Hazmats, on the one hand, and immense volume of shipments accounting for more than hundred tons in North America and Europe, on the other, we can safely state that the number of scholarly articles and dissertations have not been proportional to the significance of the subject of interest. On this ground, we conducted our research to contribute towards further developing the domain of Hazmats transportation, and sustainable supply chain management (SSCM), in general terms. Transportation of Hazmats, from logistical standpoint, may include all modes of transport via air, marine, road and rail, as well as intermodal transportation systems. Although road shipment is predominant in most of the literature, railway transportation of Hazmats has proven to be a potentially significant means of transporting dangerous goods with respect to both economies of scale and risk of transportation; these factors, have not just given rise to more thoroughly investigation of intermodal transportation of Hazmats using road and rail networks, but has encouraged the competition between rail and road companies which may indeed have some inherent advantages compared to the other medium due to their infrastructural and technological backgrounds. Truck shipment has ostensibly proven to be providing more flexibility; trains, per contra, provide more reliability in terms of transport risk for conveying Hazmats in bulks. In this thesis, in consonance with the aforementioned motivation, we provide an introduction into the hazardous commodities shipment through rail network in the first chapter of the thesis. Providing relevant statistics on the volume of Hazmat goods, number of accidents, rate of incidents, and rate of fatalities and injuries due to the incidents involving Hazmats, will shed light onto the significance of the topic under study. As well, we review the most pertinent articles while putting more emphasis on the state-of-the-art papers, in chapter two. Following the discussion in chapter 3 and looking at the problem from carrier company’s perspective, a mixed integer quadratically constraint problem (MIQCP) is developed which seeks for the minimization of transportation cost under a set of constraints including those associating with Hazmats. Due to the complexity of the problem, the risk function has been piecewise linearized using a set of auxiliary variables, thereby resulting in an MIP problem. Further, considering the interests of both carrier companies and regulatory agencies, which are minimization of cost and risk, respectively, a multiobjective MINLP model is developed, which has been reduced to an MILP through piecewise linearization of the risk term in the objective function. For both single-objective and multiobjective formulations, model variants with bifurcated and nonbifurcated flows have been presented. Then, in chapter 4, we carry out experiments considering two main cases where the first case presents smaller instances of the problem and the second case focuses on a larger instance of the problem. Eventually, in chapter five, we conclude the dissertation with a summary of the overall discussion as well as presenting some comments on avenues of future work

Evolutionary computing for routing and scheduling applications

Ph.DDOCTOR OF PHILOSOPH

Abordagens heurísticas para o planeamento de rotas e carregamento de veículos

Tese de mestrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 199

Comparativa de modelos y solvers para la optimización de variantes de problemas de rutas de vehículos

Los problemas de rutas de vehículos son uno de los casos más comunes en optimización, abarcando prácticamente cualquier tipo de transporte, en orden de mejorar la calidad del mismo. En el presente Trabajo de Fin de Grado se evaluarán los principales tipos de problemas de rutas de vehículos (incluyendo problemas con ventanas de tiempo y con recogidas y distribuciones), para cada uno de los cuáles se revisará el estado del arte de los principales modelos de optimización existentes, formulando dichos modelos y resolviéndolos con varios solvers para una batería de problemas dada. De esta forma, se pretende realizar una profunda comparación de los resultados obtenidos, consiguiendo identificar los mejores modelos y solvers para resolver cada uno de esos problemas de rutas. Por último, para algunos casos, se proponen mejoras en los modelos que permiten la obtención de unos mejores resultados, reduciendo los costes de operación asociados.Departamento de Estadística e Investigación OperativaGrado en Ingeniería en Organización Industria

A Heuristic for the Vehicle Routing Problem with Time Windows

In this paper we propose a heuristic algorithm to solve the Vehicle Routing Problem with Time Windows. Its framework is a smart combination of three simple procedures: the classical k-opt exchanges improve the solution, an ad hoc procedure reduces the number of vehicles and a second objective function drives the search out of local optima. No parameter tuning is required and no random choice is made: these are the distinguishing features with respect to the recent literature. The algorithm has been tested on benchmark problems which prove it to be more effective than comparable algorithms