6,056 research outputs found
The Split Delivery Vehicle Routing Problem with Time Windows and Customer Inconvenience Constraints
In classical routing problems, each customer is visited exactly once. By contrast, when allowing split deliveries, customers may be served through multiple visits. This potentially results in substantial savings in travel costs. Even if split deliveries are beneficial to the transport company, several visits may be undesirable on the customer side: at each visit the customer has to interrupt his primary activities and handle the goods receipt. The contribution of the present paper consists in a thorough analysis of the possibilities and limitations of split delivery distribution strategies. To this end, we investigate two different types of measures for limiting customer inconvenience (a maximum number of visits and the temporal synchronization of deliveries) and evaluate the impact of these measures on carrier efficiency by means of different objective functions (comprising variable routing costs, costs related to route durations, fixed fleet costs). We consider the vehicle routing problem with time windows in which split deliveries are allowed (SDVRPTW) and define the corresponding generalization that takes into account customer inconvenience constraints (SDVRPTW-IC). We design an extended branch-and-cut algorithm to solve the SDVRPTW-IC and report on experimental results showing the impact of customer inconvenience constraints. We finally draw useful insights for logistics managers on the basis of the experimental analysis carried out
A Tabu Search algorithm for the vehicle routing problem with discrete split deliveries and pickups
The Vehicle Routing Problem with Discrete Split Deliveries and Pickups is a variant of the Vehicle Routing Problem with Split Deliveries and Pickups, in which customers’ demands are discrete in terms of batches (or orders). It exists in the practice of logistics distribution and consists of designing a least cost set of routes to serve a given set of customers while respecting constraints on the vehicles’ capacities. In this paper, its features are analyzed. A mathematical model and Tabu Search algorithm with specially designed batch combination and item creation operation are proposed. The batch combination operation is designed to avoid unnecessary travel costs, while the item creation operation effectively speeds up the search and enhances the algorithmic search ability. Computational results are provided and compared with other methods in the literature, which indicate that in most cases the proposed algorithm can find better solutions than those in the literature
Tactical Problems in Vehicle Routing Applications
The class of Vehicle Routing Problems (VRPs) is one the most
studied topics in the Operations Research community. The vast
majority of the published papers focus on single-period problems,
with a few branches of the literature considering multiperiod
generalisations. All of these problems though, consider a short
horizon and aim at optimising the decisions at an operational
level, i.e. that will have to be taken in the near future. One
step above are tactical problems, i.e. problems concerning a
longer time horizon. Tactical problems are of a fundamental
importance as they directly influence the daily operations, and
therefore a part of the incurred costs, for a long time. The main
focus of this thesis is to study tactical problems arising in
routing applications. The first problem considered concerns the
design of a fleet of vehicles. Transportation providers often
have to design a fleet that will be used for daily operations
across a long-time span. Trucks used for transportation are very
expensive to purchase, maintain or hire. On the other side, the
composition of the fleet strongly influences the daily plans, and
therefore costs such as fuel or drivers’ wages. Balancing these
two components is challenging, and optimisation models can lead
to substantial savings or provide a useful basis for informed
decisions.
The second problem presented focuses on the use of a split
deliveries policy in multi-period routing problems. It is known
that the combined optimisation of delivery scheduling and routing
can be very beneficial, and lead to significant reductions in
costs. However, it also adds complexity to the model. The same is
true when split deliveries are introduced. The problem studied
considers the possibility of splitting the deliveries over
different days. An analysis, both theoretical and numerical, of
the impact of this approach on the overall cost is provided.
Finally, a districting problem for routing applications is
considered. These types of problems typically arise when
transportation providers wish to increase their service
consistency. There are several reasons a company may wish to do
so: to strengthen the customer-driver relationship, to increase
drivers’ familiarity with their service area, or, to simplify
the management of the service area. A typical approach,
considered here, is to divide the area under consideration in
sectors that will be subsequently assigned to specific drivers.
This type of problem is inherently of a multi-period and tactical
nature. A new formulation is proposed, integrating standard
routing models into the design of territories. This makes it
possible to investigate how operational constraints and other
requirements, such as having a fair workload division amongst
drivers, influence the effectiveness of the approach. An analysis
of the cost of districting, in terms of increased routing cost
and decreased routing flexibility, and of several operational
constraints, is presented
Proactive Highly Ambulatory Sensor Routing (PHASeR) protocol for mobile wireless sensor networks
This paper presents a novel multihop routing protocol for mobile wireless sensor networks called PHASeR (Proactive Highly Ambulatory Sensor Routing). The proposed protocol
uses a simple hop-count metric to enable the dynamic and robust routing of data towards the sink in mobile environments. It is motivated by the application of radiation mapping by unmanned vehicles, which requires the reliable and timely delivery of regular measurements to the sink. PHASeR maintains a gradient metric in mobile environments by using a global TDMA MAC layer. It also uses the technique of blind forwarding to pass messages through the network in a multipath manner. PHASeR is analysed mathematically based on packet delivery ratio, average packet delay, throughput and overhead. It is then simulated with varying mobility, scalability and traffic loads. The protocol gives good results over all measures, which suggests that it may also be suitable for a wider array of emerging applications
A MATHEMATICAL FRAMEWORK FOR OPTIMIZING DISASTER RELIEF LOGISTICS
In today's society that disasters seem to be striking all corners of the globe, the importance of emergency management is undeniable. Much human loss and unnecessary destruction of infrastructure can be avoided with better planning and foresight. When a disaster strikes, various aid organizations often face significant problems of transporting large amounts of many different commodities including food, clothing, medicine, medical supplies, machinery, and personnel from several points of origin to a number of destinations in the disaster areas. The transportation of supplies and relief personnel must be done quickly and efficiently to maximize the survival rate of the affected population.
The goal of this research is to develop a comprehensive model that describes the integrated logistics operations in response to natural disasters at the operational level. The proposed mathematical model integrates three main components. First, it controls the flow of several relief commodities from sources through the supply chain until they are delivered to the hands of recipients. Second, it considers a large-scale unconventional vehicle routing problem with mixed pickup and delivery schedules for multiple transportation modes. And third, following FEMA's complex logistics structure, a special facility location problem is considered that involves four layers of temporary facilities at the federal and state levels. Such integrated model provides the opportunity for a centralized operation plan that can effectively eliminate delays and assign the limited resources in a way that is optimal for the entire system.
The proposed model is a large-scale mixed integer program. To solve the model, two sets of heuristic algorithms are proposed. For solving the multi-echelon facility location problem, four heuristic approaches are proposed. Also four heuristic algorithms are proposed to solve the general integer vehicle routing problem. Overall, the proposed heuristics could efficiently find optimal or near optimal solution in minutes of CPU time where solving the same problems with a commercial solver needed hours of computation time.
Numerical case studies and extensive sensitivity analysis are conducted to evaluate the properties of the model and solution algorithms. The numerical analysis indicated the capabilities of the model to handle large-scale relief operations with adequate details. Solution algorithms were tested for several random generated cases and showed robustness in solution quality as well as computation time
A flexible metaheuristic framework for solving rich vehicle routing problems
Route planning is one of the most studied research topics in the operations research area. While the standard vehicle routing problem (VRP) is the classical problem formulation, additional requirements arising from practical scenarios such as time windows or vehicle compartments are covered in a wide range of so-called rich VRPs. Many solution algorithms for various VRP variants have been developed over time as well, especially within the class of so-called metaheuristics. In practice, routing software must be tailored to the business rules and planning problems of a specific company to provide valuable decision support. This also concerns the embedded solution methods of such decision support systems. Yet, publications dealing with flexibility and customization of VRP heuristics are rare. To fill this gap this thesis describes the design of a flexible framework to facilitate and accelerate the development of custom metaheuristics for the solution of a broad range of rich VRPs.
The first part of the thesis provides background information to the reader on the field of vehicle routing problems and on metaheuristic solution methods - the most common and widely-used solution methods to solve VRPs. Specifically, emphasis is put on methods based on local search (for intensification of the search) and large neighborhood search (for diversification of the search), which are combined to hybrid methods and which are the foundation of the proposed framework.
Then, the main part elaborates on the concepts and the design of the metaheuristic VRP framework. The framework fulfills requirements of flexibility, simplicity, accuracy, and speed, enforcing the structuring and standardization of the development process and enabling the reuse of code. Essentially, it provides a library of well-known and accepted heuristics for the standard VRP together with a set of mechanisms to adapt these heuristics to specific VRPs. Heuristics and adaptation mechanisms such as templates for user-definable checking functions are explained on a pseudocode level first, and the most relevant classes of a reference implementation using the Microsoft .NET framework are presented afterwards.
Finally, the third part of the thesis demonstrates the use of the framework for developing problem-specific solution methods by exemplifying specific customizations for five rich VRPs with diverse characteristics, namely the VRP with time windows, the VRP with compartments, the split delivery VRP, the periodic VRP, and the truck and trailer routing problem. These adaptations refer to data structures and neighborhood search methods and can serve as a source of inspiration to the reader when designing algorithms for new, so far unstudied VRPs. Computational results are presented to show the effectiveness and efficiency of the proposed framework and methods, which are competitive with current state-of-the-art solvers of the literature. Special attention is given to the overall robustness of heuristics, which is an important aspect for practical application
REVISIĂ“N DE LA LITERATURA DEL PROBLEMA DE RUTEO DE VEHĂŤCULOS EN UN CONTEXTO DE TRANSPORTE VERDE
In the efficient management of the supply chain the optimal management of transport of consumables and finished products appears. The costs associated with transport have direct impact on the final value consumers must pay, which in addition to requiring competitive products also demand that they are generated in environmentally friendly organizations. Aware of this reality, this document is intended to be a starting point for Master's and Doctoral degree students who want to work in a line of research recently proposed: green routing. The state of the art of the vehicle routing problem is presented in this paper, listing its variants, models and methodologies for solution. Furthermore, the proposed interaction between variants of classical routing problems and environmental effects of its operations, known in the literature as Green-VRP is presented. The goal is to generate a discussion in which mathematical models and solution strategies that can be applied within organizations that consider within their objectives an efficient and sustainable operation are posed. En el gerenciamiento eficiente de la cadena de suministro aparece la gestiĂłn Ăłptima del transporte de insumos y productos terminados. Los costos asociados al transporte tienen impacto directo sobre el valor final que deben pagar los consumidores, que además de requerir productos competitivos tambiĂ©n exigen que los mismos sean generados en organizaciones amigables con el medioambiente. Consientes de esa realidad este documento pretende ser un punto de partida para estudiantes de maestrĂa y doctorado que quieran trabajar en una lĂnea de investigaciĂłn propuesta recientemente: el ruteo verde. En este trabajo se muestra un estado del arte del problema de ruteo de vehĂculos, enumerando sus variantes, modelos y metodologĂas de soluciĂłn. Además, se presenta la interacciĂłn que se ha propuesto entre variantes clásicas de los problemas de ruteo y los efectos ambientales de su operaciĂłn, denominados en la literatura como Green-VRP. El objetivo es generar una discusiĂłn donde se planteen modelos matemáticos y estrategias de soluciĂłn que puedan ser aplicadas en organizaciones que consideren dentro de sus objetivos una operaciĂłn eficiente y sustentable.
Document type: Articl
- …