An investigation into a new class of vehicle routing problem with backhauls

A new version of the vehicle routing problem with backhauls is presented. In this new problem backhauls are not restricted to be visited once all linehaul customers have been served, neither are backhaul customers fully mixed with linehaul customers. In this problem the user based on his or her experience, the vehicle capacity, the type of products and the type of vehicle used, can define the position along a route from which the first backhaul customer may be visited. An insertion-type heuristic is put forward for this class of problems. An analysis of the improvement in route cost obtained by allowing a relaxation in the restriction of the mix of linehaul and backhaul customers is reported.     

A visual interactive approach to classical and mixed vehicle routing problems with backhauls

In this paper a new visual interactive approach for the classical vehicle routing problem with backhauls (VRPB) and its extensions is presented. The classical VRPB is the problem of designing minimum cost routes from a single depot to two type customers that are known as Backhaul (pickup) and Linehaul (delivery) customers where deliveries after pickups are not allowed. The mixed VRPB is an extension of the classical VRPB where deliveries after pickups are allowed.     

考虑差异化服务时间的多车型电动汽车路径优化与充电策略研究

在政府政策大力支持以及社会环境意识不断增长的背景下，电动汽车在物流配送行业快速普及。电动汽车参与的物流配送服务需要物流专员、电动汽车和顾客三方协作完成。因此，在传统车辆配送路径优化的基础上，车辆的多样性、充电策略、人车的匹配以及服务时间差异化等因素都会影响物流运营成本。本文提出了考虑差异化服务成本的多车型电动汽车路径优化与充电策略问题并建立了该问题的整数规划数学模型。其次，提出了混合启发式算法MCWGATS，并通过多组算例验证了算法的有效性。最后，采用多组算例分析了多车型和差异化服务时间对运营成本的影响。实验结果表明，该模型有助于物流企业提高人员、物流车辆、服务时间等资源的利用效率，降低运营成本。     

Distribution with Quality of Service Considerations: The Capacitated Routing Problem with Profits and Service Level Requirements

Inspired by a problem arising in cash logistics, we propose the Capacitated Routing Problem with Profits and Service Level Requirements (CRPPSLR). The CRPPSLR extends the class of Routing Problems with Profits by considering customers requesting deliveries to their (possibly multiple) service points. Moreover, each customer imposes a service level requirement specifying a minimum-acceptable bound on the fraction of its service points being delivered. A customer-specific financial penalty is incurred by the logistics service provider when this requirement is not met. The CRPPSLR consists in finding vehicle routes maximizing the difference between the collected revenues and the incurred transportation and penalty costs in such a way that vehicle capacity and route duration constraints are met. A fleet of homogeneous vehicles is available for serving the customers. We design a branch-and-cut algorithm and evaluate the usefulness of valid inequalities that have been effectively used for the capacitated vehicle routing problem and, more recently, for other routing problems with profits. A real-life case study taken from the cash supply chain in the Netherlands highlights the relevance of the problem under consideration. Computational results illustrate the performance of the proposed solution approach under different input parameter settings for the synthetic instances. For instances of real-life problems, we distinguish between coin and banknote distribution, as vehicle capacities only matter when considering the former. Finally, we report on the effectiveness of the valid inequalities in closing the optimality gap at the root node for both the synthetic and the real-life instances and conclude with a sensitivity analysis on the most significant input parameters of our model.     

Planning a sustainable reverse logistics system: Balancing costs with environmental and social concerns

The present work aims to support tactical and operational planning decisions of reverse logistics systems while considering economic, environmental and social objectives. In the literature, when addressing such systems economic aspects have been often used, while environmental concerns have emerged only recently. The social component is the one less studied and rarely the combination of the three concerns has been analyzed. This work considers the three objectives and was motivated by the challenge of supporting decision makers when managing a real case study of a recyclable waste collection system, where strategic decisions on the number and location of depots, vehicles and containers were taken beforehand. Tactical and operational decisions are studied involving the establishment of service areas for each depot and the definition and scheduling of collection routes for each vehicle. Such decisions should represent a compromise solution between the three objectives translating a sustainable reverse logistics plan. The problem is modeled as a multi-objective, multi-depot periodic vehicle routing problem with inter-depot routes. A mathematical formulation and a solution approach are proposed. An approximation to the Pareto front is obtained for the case study and the trade-offs between the objectives are discussed. A balanced solution is proposed.     

考虑自取服务和门到门服务的电动汽车物流网络优化策略研究

在环境意识增长与政府政策支持的有利条件下,电动汽车在物流领域得以快速发展。为提高物流服务的效率,降低企业运营成本,文中研究了考虑顾客服务策略的电动物流汽车服务设施选址与配送路径问题。采取顾客自行取货与配送人员送货上门相结合的多样化服务策略,使得服务站点的建设成本、顾客点配送路径成本以及服务站点补货路径成本之和最小。建立了整数规划数学模型,允许配送车辆在服务过程中前往服务站点接受充电服务。其次,提出了基于改进节约算法和禁忌算法的混合启发式算法MCWSA-TS。随后,在小规模算例将CPLEX运算结果与MCWSA-TS进行对比,证明了算法的有效性。最后,采用多组算例探讨了顾客取货半径对运营成本的影响,并对分离配送策略与联合配送策略进行对比分析。实验结果表明,多样化服务策略有助于企业满足顾客取货时间和取货方式的个性化需求。同时,兼顾运营成本与顾客满意度,促进电动汽车参与的物流服务快速发展。     

基于随机运输路径选择的物流中心选址模型

旨在以物流系统总费用最小化为目标进行物流中心选址规划.政府做出物流中心选址规划后,客户会选择合适的供应商进行交易,并根据已有物流中心与交通流分布进行货物运输路线决策,使其总费用最少.论文提出了物流中心选址双层规划模型,考虑投资费用的约束,保证用户平衡的同时使整个物流系统总费用最低.其中上层规划目标是使物流系统总费用最小化,下层规划建立了一个Logit随机用户均衡模型,并构造了一个等价的凸规划问题.最后针对模型提出了一个算法,并通过算例说明其可行性.     

A continuous-time supply-driven inventory-constrained routing problem

We address an inventory routing problem (IRP) in which routing and inventory decisions are dictated by supply rather than demand. Moreover, inventory is held in containers that act as both a storage container and a movable transport unit. This problem emanates from logistics related to biogas transportation in which biogas is transported in containers from many suppliers to a single facility. We present a novel and compact formulation for the supply-driven IRP which addresses the routing decisions in continuous-time in which inventory levels within the containers are continuous. Valid inequalities are included and realistic instances are solved to optimality. For all experiments, we found that the total transportation time is minimized when the storage capacity at each supplier is larger than or equal to the vehicle capacity. These routes are characterized by tours in which mostly single suppliers are visited. In 95% of the instances, the average content level of the exchanged containers exceeded 99.6%.     

A comparative study of formulations for a cross-dock door assignment problem

A cross docking facility is a type of warehouse in supply chain management that allows orders to be prepared with or without going through the phase of storing products in the warehouse and subsequently selecting them for delivery. The goods are unloaded from incoming trucks called origins on inbound doors of a cross-docking facility platform and, using a handling device inside the platform such as a forklift, immediately transferred to outbound doors to be loaded into outgoing trucks named destinations or delivery trucks for distribution to customers. Contrary to a traditional warehouse, goods are unloaded and loaded without placing them in temporary storage inside the cross-docking facility. The goal of the cross-docking assignment problem (CDAP) is to assign origins to inbound doors and destinations to outbound doors so that the total cost inside the cross-dock platform is minimized. To the best of our knowledge, there are only three mixed integer programming (MIP) formulations of the CDAP in the literature. We propose eight new MIP models and demonstrate the mathematical equivalence of all 11 models, together with rigorously proving some of their properties. In order to detect which of these 11 models is best, we conduct an extensive comparative analysis on benchmark instances from the literature, which discloses that the best model is one proposed in this paper for the first time.     

Cross-docking: State of the art

Cross-docking is a logistics strategy in which freight is unloaded from inbound vehicles and (almost) directly loaded into outbound vehicles, with little or no storage in between. This paper presents an overview of the cross-docking concept. Guidelines for the successful use and implementation of cross-docking are discussed and several characteristics are described that can be used to distinguish between different cross-dock types. In addition, this paper presents an extensive review of the existing literature about cross-docking. The discussed papers are classified based on the problem type that is tackled (ranging from more strategic or tactical to more operational problems). Based on this review, several opportunities to improve and extend the current research are indicated.     

A reactive tabu search algorithm for the vehicle routing problem with simultaneous pickups and deliveries

The vehicle routing problem with pickups and deliveries (VRPPD) extends the vehicle routing problem (VRP) by allowing customers to both send and receive goods. The main difficulty of the problem is that the load of vehicles is fluctuating rather than decreasing as in the VRP. We design a reactive tabu search metaheuristic that can check feasibility of proposed moves quickly and reacts to repetitions to guide the search. Several new best solutions are found for benchmark problems.     

Cross dock scheduling: Classification,literature review and research agenda

At cross docking terminals incoming deliveries of inbound trucks are unloaded, sorted, moved across the dock and finally loaded onto outbound trucks, which immediately leave the terminal towards their next destination in the distribution chain. Accordingly, a cross dock is a consolidation point in a distribution network, where multiple smaller shipments can be merged to full truck loads in order to realize economies in transportation. In this context, the truck scheduling problem, which decides on the succession of truck processing at the dock doors, is especially important to ensure a rapid turnover and on-time deliveries. Due to its high real-world significance, several truck scheduling procedures have been introduced during recent years, which all treat specific cross dock settings. In order to structure and promote scientific progress, this paper introduces a classification of deterministic truck scheduling. With the help of this classification, existing literature is reviewed and future research needs are identified. Moreover, we represent a yet unexplored class of truck scheduling problems which is highly relevant in real-world distribution networks.     

Firm-level correlates of emergent green supply chain management practices in the Chinese context

Greening the supply chain is increasingly a concern for many business enterprises and a challenge for logistics management in the 21st century. Of particular concern is how to arouse organizational environmental awareness and put environmental activities into practice in the logistics activities of their supply chains. This paper investigates the correlation of two major factors, organizational learning and management support, with the extent of adoption of green supply chain management (GSCM) practices in Chinese manufacturing firms, where their inbound and outbound logistics activities are potential polluters to the environment. Organizational and operational learning was derived from the firm's experience with programs such as total quality management and environmental management systems. Management support included support for GSCM ideas and practices from top and middle-level management and cooperation across organizational functions. We find significant positive relationships between organizational learning mechanisms, organizational support and the adoption of GSCM practices, after controlling for a number of other influences including regulations, marketing, supplier, cost pressures, industry levels of the relevant practice and organizational size. Implications of our findings on logistics management are discussed.     

回载可分的闭环供应链多配送中心多车辆运输策略

本文从车辆路径的角度研究了具有多个配送中心、多台车辆结合前向物流配送和逆向物流回载的闭环供应链运输策略,考虑回收产品的不同形态和可分批运输的特点,引入库存限制和成本惩罚,建立并分析了问题的数学模型.运用sweep算法把多配送中心转化为单配送中心,引入2σ原则构造了分组的启发式求解方法.算例分析表明该策略的合理有效性.     

Flexible time window management for attended home deliveries

In the competitive world of online retail, customers can choose from a selection of delivery time windows on a retailer’s website. Creating a set of suitable and cost-efficient delivery time windows is challenging, since customers want short time windows, but short time windows can increase delivery costs significantly. Furthermore, the acceptance of a request in a short time window can greatly restrict the ability to accommodate future requests. In this paper, we present customer acceptance mechanisms that enable flexible time window management in the booking of time-window based attended home deliveries. We build tentative delivery routes and check which time windows are feasible for each new customer request. We offer the feasible long delivery time windows and let our approaches decide when to offer short time windows. Our approaches differ in the information they consider with regard to customer characteristics as well as detailed characteristics of the evolving route plan. We perform a computational study to investigate the approaches’ ability to offer short time windows and still allow for a large number of customers to be served. We consider various demand scenarios, partially derived from real order data provided by a German online supermarket.     

有顾客时间窗和发货量变化的车辆调度干扰管理研究

为解决由顾客需求变化引发的物流配送干扰问题,提出基于干扰管理思想构建扰动恢复策略和方案.应用虚拟多车场实现车辆调度扰动恢复问题转化.提出车辆调度扰动恢复策略和扰动度量方法,以作为车辆调度干扰管理建模的基础;分析顾客时间窗和发货量变化造成的扰动并进行辨识.建立相应的干扰管理模型,提出归一化处理办法对VRPTW、MD-VRPTW和MDVRPTW干扰管理问题进行有效兼容;结合干扰管理模型的特点,改进基于顾客的编码表示方法,可以反映出车辆调度扰动恢复策略;根据干扰管理思想,设计遗传算法对干扰管理模型进行求解.给出了一个具有代表性的算例试验结果,算例结果及其分析表明干扰管理模型和遗传算法的有效性.     

基于改进差分进化算法的VRP-SDPTW研究

整合前向物流和逆向物流,提出带时间窗的同时送货和取货的车辆路径问题(VRP-SDPTW)的混合整数规划数学模型.首次提出改进的差分进化算法(IDE)求解该问题,算法对不可行解设计惩罚机制,当基因值超过规定的范围时,设计基于整数序规范的辅助算子解决变异问题,设计一种随进化代数自动更新的交叉率.数值实验表明,改进的差分进化算法能有效地求解VRP-SDPTW.     

Green logistics management and performance: Some empirical evidence from Chinese manufacturing exporters

The value chain of many business enterprises is increasingly required to demonstrate the profitability of their primary activities, starting from inbound logistics to operations, outbound logistics, marketing sales, and finally to services. The adoption of green logistics management (GLM) presents an opportunity for Chinese manufacturing exporters to competently respond to the escalating expectation of the international community for resources conservation and to achieve environmental performance profitably. This study makes several important contributions to the literature on managing logistics with environmental considerations. First, the authors identify the components of GLM: (i) procedure-based practices, (ii) evaluation-based practices, (iii) partner-based practices, and (iv) general environmental management practices. Second, they relate GLM to environmental and operational performance in a developing country context. Third, they identify the institutional and operational antecedents that prompt the adoption of GLM by export-oriented manufacturing enterprises in China. Fourth, they examine the moderating effect of environmental regulatory pressure on the GLM-performance linkage. The results are based on a survey of manufacturing exporters in China. The commonly held view that economic motivation is related to the adoption of GLM is not supported. However, GLM positively affects both environmental and operational performance, and regulatory pressure enhances the GLM-performance relationship.     

供需未匹配的多车场多车型多货品可拆分取送货车辆路径问题

取送货车辆路径问题在多点调拨系统普遍存在,属于NP-hard问题。该问题研究通常需考虑车场数、车型种类、货品种类、客户服务次数等诸多因素,已有文献多假设客户间供需已匹配、单车场、单车型、单货品和取送货需求一次性满足,优化目标多设置为总路径最短。而从企业运营实践来看,运输方案不仅要规划客户间访问路径,还需进行客户间供需匹配;运输成本不仅与运距有关,还涉及运输货品的重量和派车成本;运输网络中多车场、多车型和多货品更加常见,且客户需求量往往大于车辆装载能力。因此,本文首次尝试基于"运距×运量"的车辆路径成本和基于额定吨位的固定派车成本之和最小为优化目标,建立同时考虑多车场、多车型、多货品、客户间供需未匹配和需求可拆分的取送货车辆路径问题模型,并设计基于大规模邻域搜索的迭代局部搜索求解算法。该算法采用基于运输效率提升的贪婪思想来快速构建高质量初始可行解,并通过引入四种移除算子、两种修复算子和车场车型调整优化策略形成大规模可行搜索邻域以增强全局寻优能力。基于18个文献算例和6个企业实例的数值实验结果表明：1）本文提出的算法在求解质量和求解效率方面均优于相关文献中的算法;2）相对人工调拨方案,本文设计的方案能够帮助企业节约33%的运输成本和21%的车次。本研究不仅可拓展取送货车辆路径问题现有理论,而且可为企业实际运营提供决策支持。     

A heuristic algorithm for the period vehicle routing problem

In this paper we consider the period vehicle routing problem, which is the problem of designing routes for delivery vehicles to meet customer service level requirements (not all customers require delivery on every day in the period). A heuristic algorithm, based upon the daily vehicle routing algorithm of Fisher and Jaikumar, is presented and computational results are given for test problems drawn from the literature.