Two traveling salesman facility location problems

Includes bibliographical references.Work partially supported by the National Science Foundation. ECS-8717970Dimitris Bertsimas

How many fast-charging stations do we need along European highways?

For a successful market take-up of plug-in electric vehicles, fast-charging stations along the highway network play a significant role. This paper provides results from a first study on estimating the minimum number of fast-charging stations along the European highway network of selected countries (i.e., France, Germany, the Benelux countries, Switzerland, Austria, Denmark, the Czech Republic, and Poland) and gives an estimate on their future profitability. The combination of a comprehensive dataset of passenger car trips in Europe and an efficient arc-coverpath-cover flow-refueling location model allows generating results for such a comprehensive transnational highway network for the first time. Besides the minimum number of required fastcharging stations which results from the applied flow-refueling location model (FRLM), an estimation of their profitability as well as some country-specific results are also identified. According to these results the operation of fast-charging stations along the highway will be attractive in 2030 because the number of customers per day and their willingness to pay for a charge is high compared to inner-city charging stations. Their location-specific workloads as well as revenues differ significantly and a careful selection of locations is decisive for their economic operation

A priori optimization

Includes bibliographical references.Partially supported by the National Science Foundation. ECS-8717970Dimitris J. Bertsimas, Patrick Jaillet and Amedeo R. Odoni

An Alternative Fuel Refueling Station Location Model considering Detour Traffic Flows on a Highway Road System

With the development of alternative fuel (AF) vehicle technologies, studies on finding the potential location of AF refueling stations in transportation networks have received considerable attention. Due to the strong limited driving range, AF vehicles for long-distance intercity trips may require multiple refueling stops at different locations on the way to their destination, which makes the AF refueling station location problem more challenging. In this paper, we consider that AF vehicles requiring multiple refueling stops at different locations during their long-distance intercity trips are capable of making detours from their preplanned paths and selecting return paths that may be different from original paths for their round trips whenever AF refueling stations are not available along the preplanned paths. These options mostly need to be considered when an AF refueling infrastructure is not fully developed on a highway system. To this end, we first propose an algorithm to generate alternative paths that may provide the multiple AF refueling stops between all origin/destination (OD) vertices. Then, a new mixed-integer programming model is proposed to locate AF refueling stations within a preselected set of candidate sites on a directed transportation network by maximizing the coverage of traffic flows along multiple paths. We first test our mathematical model with the proposed algorithm on a classical 25-vertex network with 25 candidate sites through various scenarios that consider a different number of paths for each OD pair, deviation factors, and limited driving ranges of vehicles. Then, we apply our proposed model to locate liquefied natural gas refueling stations in the state of Pennsylvania considering the construction budget. Our results show that the number of alternative paths and deviation distance available significantly affect the coverage of traffic flows at the stations as well as computational time

Solución de problemas estocásticos de localización-ruteo

96 Páginas.El problema de localización-ruteo estocástico (SLRP por sus siglas en inglés) es un problema muy común en empresas de manufactura, comercializadoras y transportadoras. El problema consiste en simultáneamente localizar uno o varios depósitos centrales entre un conjunto de ubicaciones potenciales, determinar un tamaño de flota y diseñar rutas para cada unos de los vehículos para visitar un conjunto de clientes considerando la incertidumbre que existe en algunos aspectos de la operación. En las soluciones presentadas en la literatura para este tipo de problemas se ha considerado mayoritariamente soluciones determinísticas o las soluciones estocásticas presentadas solo consideran en su mayoría la demanda como componente estocástico del sistema. La presente investigación propone un modelo para resolver la versión estocástica con incertidumbre en los costos de transporte y velocidades de los vehículos a través de un enfoque jerárquico de dos fases basado tanto en optimización como en simulación de eventos discretos. Se presenta una estrategia de selección aleatoria en la fase de localización; la fase de ruteo se resuelve empleando un algoritmo basado en colonia de hormigas, y finalmente se incluye al modelo el comportamiento estocástico del sistema a través de simulación de eventos discretos. Se presenta un análisis comparativo para validar la calidad de las soluciones obtenidas por el algoritmo y se realiza un estudio experimental permitiendo el análisis estadístico de resultados. Los resultados obtenidos permiten validar el presente enfoque como una buena herramienta de apoyo a la toma de decisiones para la localización de centros de distribución, la determinación de flotas de vehículos, la asignación de zonas de servicio y el ruteo de vehículos

Addressing freight imbalance in the truckload trucking industry through hierarchical planning.

Freight imbalance is a problem that negatively affects drivers and carriers within the truckload trucking industry. One result of this problem is that the industry experiences high annual driver turnover, exceeding 130% annually. The turnover can be attributed in part to driver dissatisfaction due to the inability of the carriers to provide regular driving tours as a result of freight imbalance. However, due to the complexity of the imbalance, carriers have difficulty combating the problem. This dissertation examines three problems addressing freight imbalance from a hierarchical planning perspective. The Weekend Draying Problem focuses is an operational planning approach for addressing weekend truckload dispatching. The application of this methodology to a nationwide trucking network reveals that a carrier can experience significant customer service improvements while at the same time meeting the needs and expectations of their drivers. As a result, more regular driving tours can be established. The Driver Domicile Problem uses tactical planning to examine nationwide driver recruitment strategies. With driver turnover and driver retention imposing significant burdens on the truckload trucking industry, the proposed strategy reveals key locations where a potential driver base could be recruited that would improve the carrier\u27s ability to provide the drivers with more regular tours and frequent get home opportunities. Results highlight which factors contribute to the best design of a nationwide domicile plan. The Distribution Center Location Problem is a strategic plan for the design of various sized distribution networks that minimize trucking costs without affecting delivery requirements. Whereas historical design focused on time and distance minimization, these networks address freight imbalance by focusing on cost minimization. Examination and analysis of these problems is conducted through discrete event system simulation, computer modeling, and mathematical programming. Outcomes from the research of these problems are industrially relevant. The application of these methodologies will assist the truckload trucking carriers in dealing with inherent freight imbalance issues and helping them overcome many challenges they face. Collectively this dissertation demonstrates ways to address freight imbalance both in the short term planning horizon and the long term planning horizon

Enabling long journeys in electric vehicles:design and demonstration of an infrastructure location model

This research develops a methodology and model formulation which suggests locations for rapid chargers to help assist infrastructure development and enable greater battery electric vehicle (BEV) usage. The model considers the likely travel patterns of BEVs and their subsequent charging demands across a large road network, where no prior candidate site information is required. Using a GIS-based methodology, polygons are constructed which represent the charging demand zones for particular routes across a real-world road network. The use of polygons allows the maximum number of charging combinations to be considered whilst limiting the input intensity needed for the model. Further polygons are added to represent deviation possibilities, meaning that placement of charge points away from the shortest path is possible, given a penalty function. A validation of the model is carried out by assessing the expected demand at current rapid charging locations and comparing to recorded empirical usage data. Results suggest that the developed model provides a good approximation to real world observations, and that for the provision of charging, location matters. The model is also implemented where no prior candidate site information is required. As such, locations are chosen based on the weighted overlay between several different routes where BEV journeys may be expected. In doing so many locations, or types of locations, could be compared against one another and then analysed in relation to siting practicalities, such as cost, land permission and infrastructure availability. Results show that efficient facility location, given numerous siting possibilities across a large road network can be achieved. Slight improvements to the standard greedy adding technique are made by adding combination weightings which aim to reward important long distance routes that require more than one charge to complete

Optimization of an inductive charging infrastructure for urban road traffic

Mit sinkenden fossilen Energiereserven und weltweit steigendem Mobilitätsbedarf steht unserer Gesellschaft auf lange Sicht die Abkehr von fossilen Energieträgern bevor. Die Energiedichte von alternativen Energieträgern liegt deutlich unter der von Erdöl. Bei deren Anwendung muss berücksichtigt werden, dass das vollständige Betanken von Straßenfahrzeugen viel länger dauert und die übertragene Energiemenge für deutlich kürzere Distanzen reicht, als man es von heutigen Fahrzeugen gewohnt ist, die mit fossilen Kraftstoffen betrieben werden. Zur Aufrechterhaltung der Mobilität und schnellen Nutzerakzeptanz müssen die Folgen dieser Umstellung untersucht sowie Anforderungen und Maßnahmen abgeleitet werden, um die Einschränkungen des Verkehrsbetriebs zu minimieren. Diese Arbeit widmet sich der Fragestellung, wie viel Energie der Straßenverkehrsbetrieb erfordert und welchen Anforderungen die Energieübertragung genügen muss, damit künftige Ladeprozesse ohne Einschränkungen für Teilnehmer in den Verkehr integriert werden können. Als Grundlage für die Verkehrsbetrachtungen dienen mikroskopisch simulierte Verkehrsszenarien, deren Modelle mit Verkehrs- und Fahrzeugmessdaten kalibriert werden. Darüber hinaus wird ein zeitdiskretes Modell für die Berechnung des Fahrzeugenergiebedarfs vorgestellt und in ein mikroskopisches Verkehrssimulationswerkzeug implementiert. Die Simulationsdaten münden anschließend in einem linearen Programm, welches unter Berücksichtigung der Ladeleistung und weiteren betrieblichen Randbedingungen mit geeigneten Methoden die Anordnung der Ladestellen optimiert. Abschließend wird das vorgestellte Verfahren beispielhaft an der zu optimierenden Verortung der Komponenten einer induktiven Energieversorgungsinfrastruktur präsentiert. Die Anordnung einer neu in Betrieb zu nehmenden Infrastruktur wird auf den vorherrschenden Verkehr ausgelegt und optimiert. Trotz deutlich geringerer Fahrzeugreichweiten und Übertragungsleistungen als mit heutigen Fahrzeugen müssen Fahrer nach der erfolgten infrastrukturellen Optimierung bei ihrer Routenwahl keine dedizierten Halte für die Energieübertrag berücksichtigen. Städteplanern sowie Infrastruktur- und Flottenbetreibern wird damit erstmals ein Werkzeug und ein Verfahren zur Verfügung gestellt, mit dem vorherrschende oder zukünftige Szenarien hinsichtlich Verkehrsaufkommen und Energiebereitstellung integriert analysiert werden können.Diminishing crude oil supplies will inevitabely require the development and application of alternatives that fuel the globally increasing demand for mobility. Since the energy density of alternative energy carriers is very low compared to crude oil, the migration will be accompanied with drawbacks in user comfort like that of fully charging a vehicle in less than two minutes or of travelling distances of several hundred kilometers with a single charge. For the quick acceptance of new concepts, to maintain the current level of mobility, and to minimize the limitations on traffic operation, the consequences of using alternative energy carriers in road vehicles will have to be evaluated as well as requirements be formulated and measures be developed. This thesis deals with the amount of energy that road traffic requires and with the requirements for the energy transfer in order to integrate charging processes into traffic operation with minimum limitations. The focus lies on urban traffic, which accounts for the majority of the global traffic volume. Microscopic traffic simulations build the basis for the traffic analyses that are calibrated with traffic and vehicle measurement data. A time-discrete model will be presented and implemented in a traffic simulation tool that allows the calculation of the energy demand in simulated vehicles. A linear program will be developed that uses the simulation results and optimizes the charging station locations in consideration of the charging power and other operational boundaries. The presented technique is applied in a final step to determine the optimal arrangement of a charging infrastructure to adequately supply road traffic vehicles. The novelty of this work lies in the fact that the optimal placement of charging stations allows the integration of charging processes into traffic operation. The arrangement of the charging infrastructure is designed and optimized for prevailing traffic. It will be shown that vehicles with even lower driving ranges than today's vehicles will not require dedicated charging halts along their routes that interrupt their operations. City planners as well as infrastructure and fleet operators will further be provided with a tool and a method that allows the integrated analysis of future scenarios in regard of traffic volume and energy supply

Problemas de localização-distribuição de serviços semiobnóxios: aproximações e apoio à decisão

Doutoramento em Gestão IndustrialA presente tese resulta de um trabalho de investigação cujo objectivo se centrou no problema de localização-distribuição (PLD) que pretende abordar, de forma integrada, duas actividades logísticas intimamente relacionadas: a localização de equipamentos e a distribuição de produtos. O PLD, nomeadamente a sua modelação matemática, tem sido estudado na literatura, dando origem a diversas aproximações que resultam de diferentes cenários reais. Importa portanto agrupar as diferentes variantes por forma a facilitar e potenciar a sua investigação. Após fazer uma revisão e propor uma taxonomia dos modelos de localização-distribuição, este trabalho foca-se na resolução de alguns modelos considerados como mais representativos. É feita assim a análise de dois dos PLDs mais básicos (os problema capacitados com procura nos nós e nos arcos), sendo apresentadas, para ambos, propostas de resolução. Posteriormente, é abordada a localização-distribuição de serviços semiobnóxios. Este tipo de serviços, ainda que seja necessário e indispensável para o público em geral, dada a sua natureza, exerce um efeito desagradável sobre as comunidades contíguas. Assim, aos critérios tipicamente utilizados na tomada de decisão sobre a localização destes serviços (habitualmente a minimização de custo) é necessário adicionar preocupações que reflectem a manutenção da qualidade de vida das regiões que sofrem o impacto do resultado da referida decisão. A abordagem da localização-distribuição de serviços semiobnóxios requer portanto uma análise multi-objectivo. Esta análise pode ser feita com recurso a dois métodos distintos: não interactivos e interactivos. Ambos são abordados nesta tese, com novas propostas, sendo o método interactivo proposto aplicável a outros problemas de programação inteira mista multi-objectivo. Por último, é desenvolvida uma ferramenta de apoio à decisão para os problemas abordados nesta tese, sendo apresentada a metodologia adoptada e as suas principais funcionalidades. A ferramenta desenvolvida tem grandes preocupações com a interface de utilizador, visto ser direccionada para decisores que tipicamente não têm conhecimentos sobre os modelos matemáticos subjacentes a este tipo de problemas.This thesis main objective is to address the location-routing problem (LRP) which intends to tackle, using an integrated approach, two highly related logistics activities: the location of facilities and the distribution of materials. The LRP, namely its mathematical formulation, has been studied in the literature, and several approaches have emerged, corresponding to different real-world scenarios. Therefore, it is important to identify and group the different LRP variants, in order to segment current research and foster future studies. After presenting a review and a taxonomy of location-routing models, the following research focuses on solving some of its variants. Thus, a study of two of the most basic LRPs (capacitated problems with demand either on the nodes or on the arcs) is performed, and new approaches are presented. Afterwards, the location-routing of semi-obnoxious facilities is addressed. These are facilities that, although providing useful and indispensible services, given their nature, bring about an undesirable effect to adjacent communities. Consequently, to the usual objectives when considering their location (cost minimization), new ones must be added that are able to reflect concerns regarding the quality of life of the communities impacted by the outcome of these decisions. The location-routing of semi-obnoxious facilities therefore requires to be analysed using multi-objective approaches, which can be of two types: noninteractive or interactive. Both are discussed and new methods proposed in this thesis; the proposed interactive method is suitable to other multi-objective mixed integer programming problems. Finally, a newly developed decision-support tool to address the LRP is presented (being the adopted methodology discussed, and its main functionalities shown). This tool has great concerns regarding the user interface, as it is directed at decision makers who typically don’t have specific knowledge of the underlying models of this type of problems