Showing papers in "Transportation Research Part E-logistics and Transportation Review in 2012"

A Green Vehicle Routing Problem

Abstract: A Green Vehicle Routing Problem (G-VRP) is formulated and solution techniques are developed to aid organizations with alternative fuel-powered vehicle fleets in overcoming difficulties that exist as a result of limited vehicle driving range in conjunction with limited refueling infrastructure The G-VRP is formulated as a mixed integer linear program Two construction heuristics, the Modified Clarke and Wright Savings heuristic and the Density-Based Clustering Algorithm, and a customized improvement technique, are developed Results of numerical experiments show that the heuristics perform well Moreover, problem feasibility depends on customer and station location configurations Implications of technology adoption on operations are discussed

Sailing speed optimization for container ships in a liner shipping network

Abstract: This paper first calibrates the bunker consumption – sailing speed relation for container ships using historical operating data from a global liner shipping company. It proceeds to investigate the optimal sailing speed of container ships on each leg of each ship route in a liner shipping network while considering transshipment and container routing. This problem is formulated as a mixed-integer nonlinear programming model. In view of the convexity, non-negativity, and univariate properties of the bunker consumption function, an efficient outer-approximation method is proposed to obtain an e-optimal solution with a predetermined optimality tolerance level e. The proposed model and algorithm is applied to a real case study for a global liner shipping company.

Optimization Approach to Depot Location and Trip Selection in One-Way Carsharing Systems

Abstract: In this paper, we present an optimization approach to depot location in one-way carsharing systems where vehicle stock imbalance issues are addressed under three trip selection schemes The approach is based on mixed-integer programming models whose objective is to maximize the profits of a carsharing organization considering all the revenues and costs involved The practical usefulness of the approach is illustrated with a case study involving the municipality of Lisbon, Portugal The results we have obtained from this study provided a clear insight into the impact of depot location and trip selection schemes on the profitability of such systems

Minimizing fuel emissions by optimizing vessel schedules in liner shipping with uncertain port times

Abstract: We consider the problem of designing an optimal vessel schedule in the liner shipping route to minimize the total expected fuel consumption (and emissions) considering uncertain port times and frequency requirements on the liner schedule. The general optimal scheduling problem is formulated and tackled by simulation-based stochastic approximation methods. For special cases subject to the constraint of 100% service level, we prove the convexity and continuous differentiability of the objective function. Structural properties of the optimal schedule under certain conditions are obtained with useful managerial insights regarding the impact of port uncertainties. Case studies are given to illustrate the results.

A hierarchical clustering and routing procedure for large scale disaster relief logistics planning

Abstract: We describe a hierarchical cluster and route procedure (HOGCR) for coordinating vehicle routing in large-scale post-disaster distribution and evacuation activities. The HOGCR is a multi-level clustering algorithm that groups demand nodes into smaller clusters at each planning level, enabling the optimal solution of cluster routing problems. The routing problems are represented as capacitated network flow models that are solved optimally and independently by CPLEX on a parallel computing platform. The HOGCR preserves the consistency among parent and child cluster solutions obtained at consecutive levels. We assess the performance of the algorithm by using large scale scenarios and find satisfactory results.

Bioethanol supply chain system planning under supply and demand uncertainties

Abstract: A mixed integer stochastic programming model is established to support strategic planning of bioenergy supply chain systems and optimal feedstock resource allocation in an uncertain decision environment. The two-stage stochastic programming model, together with a Lagrange relaxation based decomposition solution algorithm, was implemented in a real-world case study in California to explore the potential of waste-based bioethanol production. The model results show that biowaste-based ethanol can be a viable part of sustainable energy solution for the future.

Shelter location and transportation planning under hurricane conditions

Abstract: This paper develops a scenario-based bilevel programming model to optimize the selection of shelter locations with explicit consideration of a range of possible hurricane events and the evacuation needs under each of those events. A realistic case study for the state of North Carolina is presented. Through the case study, we demonstrate (i) the criticality of considering multiple hurricane scenarios in the location of shelters, and; (ii) the importance of considering the transportation demands of all evacuees when selecting locations for public shelters.

Reliable design of a forward/reverse logistics network under uncertainty: A robust-M/M/c queuing model

Abstract: This paper presents a novel model for designing a reliable network of facilities in closed-loop supply chain under uncertainty. For this purpose, a bi-objective mathematical programming formulation is developed which minimizes the total costs and the expected transportation costs after failures of facilities of a logistics network. To solve the model, a new hybrid solution methodology is introduced by combining robust optimization approach, queuing theory and fuzzy multi-objective programming. Computational experiments are provided for a number of test problems using a realistic network instance.

The time dependent vehicle routing problem with time windows: Benchmark problems, an efficient solution algorithm, and solution characteristics

Abstract: An algorithm that can tackle time dependent vehicle routing problems with hard or soft time windows without any alteration in its structure is presented. Analytical and experimental results indicate that average computational time increases proportionally to the number of customers squared. New replicable test problems that capture the typical speed variations of congested urban settings are proposed. Solution quality, time window perturbations, and computational time results are discussed as well as a method to study the impact of perturbations by problem type. The algorithm efficiency and simplicity is well suited for urban areas where fast running times may be required.

Modeling closed-loop supply chains in the electronics industry: A retailer collection application

Abstract: This paper proposes a retailer collection model whereby the retailer collects end-of-life products and the manufacturer cooperates with a third-party firm to handle used products, and a non-retailer collection model whereby a third-party firm is subcontracted by the manufacturer for collection work. While the return rate, manufacturer’s profits, and channel members’ total profits of the retailer collection model are not always superior to those of the non-retailer collection model, we find that the retail collection model analytically outperforms when the third-party firm is a non-profit organization for recycling and disposal.

Liner Ship Fleet Deployment with Container Transshipment Operations

Abstract: This paper proposes a liner ship fleet deployment (LSFD) problem with container transshipment operations. The proposed problem is formulated as a mixed-integer linear programming model which allows container transshipment operations at any port, any number of times, without explicitly defining the container transshipment variables. Experiments on the Asia–Europe–Oceania shipping network of a global liner shipping company show that more than one third (17–22 ports) of the total of 46 ports have transshipment throughputs. Computational studies based on randomly generated large-scale shipping networks demonstrate that the proposed model can be solved efficiently by CPLEX.

Robust schedule design for liner shipping services

Abstract: This paper examines the design of liner ship route schedules that can hedge against the uncertainties in port operations, which include the uncertain wait time due to port congestion and uncertain container handling time. The designed schedule is robust in that uncertainties in port operations and schedule recovery by fast steaming are captured endogenously. This problem is formulated as a mixed-integer nonlinear stochastic programming model. A solution algorithm which incorporates a sample average approximation method, linearization techniques, and a decomposition scheme, is proposed. Extensive numerical experiments demonstrate that the algorithm obtains near-optimal solutions with the stochastic optimality gap less 1.5% within reasonable time.

The co-opetitive strategy of a closed-loop supply chain with remanufacturing

Abstract: This paper deals with a strategic issue of closed-loop supply chains with remanufacturing by developing analytic models under cooperative and competitive settings. The primary goal behind analytic formulation is to investigate under what conditions an original equipment manufacturer (OEM) may take a cooperative approach by participating in remanufacturing. In contrast, the OEM may take a competitive approach by letting the third-party firm remanufacture the returned cores and remarket in the secondary market that competes with the new product. Our analysis reveals that the strategic decision depends critically on the costs of remanufacturing and the competition intensity between the two versions.

A bi-objective model for planning and managing rail-truck intermodal transportation of hazardous materials

Abstract: We propose a bi-objective optimization framework for routing rail-truck intermodal shipments with hazardous materials, when shippers and receivers have access to alternate intermodal terminals. A tabu-search based solution methodology is developed, which together with the optimization framework is applied to realistic size problem instances to gain managerial insights. Our analysis indicates that drayage accounts for a significant portion of transport risk and that it can be reduced by scheduling direct and faster trains; and, that the mix of intermodal trains depends on the interest of the decision-makers, where the resulting traffic can facilitate planning emergency response systems.

A supply chain generalized network oligopoly model for pharmaceuticals under brand differentiation and perishability

Abstract: In this paper, we construct a generalized network oligopoly model with arc multipliers for supply chains of pharmaceutical products using variational inequality theory. The model captures the Cournot competition among the manufacturers who seek to determine their profit-maximizing product flows, which can be perishable, with the consumers differentiating among the products of the firms, whether branded or generic, and the firms taking into consideration the discarding costs. The numerical examples demonstrate that a brand pharmaceutical product may lose its dominant market share as a consequence of patent rights expiration and because of generic competition.

Tradable travel credits for congestion management with heterogeneous users

Abstract: This paper carries on the recent work of Yang and Wang (2011) on tradable credit schemes by considering heterogeneous users with different value of time (VOT). Given a tradable credit scheme, the user equilibrium (UE) and market equilibrium (ME) conditions with heterogeneous users are formulated into a variational inequalities (VI) problem. Sufficient conditions for uniqueness of the aggregate UE link flows and then the ME credit price are established. Appropriate tradable credit schemes are developed to decentralize system optimal and Pareto-improving network flow patterns. Extension is made to the elastic demand case.

Hierarchical multimodal hub location problem with time-definite deliveries

Abstract: Hierarchical multimodal hub location problem is a cost-minimizing hub covering problem where two types of hubs and hub links, accounting for ground and air transportation, are to be established, while ensuring time-definite deliveries. We propose a mixed-integer programming formulation and perform a comprehensive sensitivity analysis on the Turkish network. We show that the locations of airport hubs are less sensitive to the cost parameters compared to the locations of ground hubs and it is possible to improve the service quality at not much additional cost in the resulting multimodal networks. Our methodology provides the means for a detailed trade-off analysis.

The effects of corporate governance on airline performance: Production and marketing efficiency perspectives

Abstract: This study explores the relationship between operating performance and corporate governance in 30 airline companies operating in the US. First, this study applies a two-stage Data Envelopment Analysis (DEA) to evaluate the production efficiency and marketing efficiency of the airlines. Our findings indicate that, in general, there is not as much dispersion in the relative productive efficiencies of the airlines as there is in their marketing efficiencies. The low-cost airlines, on average, are more efficient carriers than the full-service ones, but less efficient marketers. Secondly, truncated regression is used to explore whether the characteristics of corporate governance affect airline performance. The results demonstrate that corporate governance influences firm performance significantly. Finally, we address the managerial decision-making matrix and make suggestions to help airline managers improve performance.

Optimal Distance Tolls under Congestion Pricing and Continuously Distributed Value of Time

Abstract: This paper addresses the optimal distance-based toll design problem for cordon-based congestion pricing schemes. The optimal distance tolls are determined by a positive and non-decreasing toll-charge function with respect to the travel distance. Each feasible toll-charge function is evaluated by a probit-based SUE (Stochastic User Equilibrium) problem with elastic demand, asymmetric link travel time functions, and continuously distributed VOT, solved by a convergent Cost Averaging (CA) method. The toll design problem is formulated as a mixed-integer mathematical programming with equilibrium constraints (MPEC) model, which is solved by a Hybrid GA (Genetic Algorithm)–CA method. Finally, the proposed models and algorithms are assessed by two numerical examples.

Linkages between customer service, customer satisfaction and performance in the airline industry: Investigation of non-linearities and moderating effects

Abstract: The paper investigates the linkages between customer service, customer satisfaction, and firm performance in the US airline industry. In particular, the moderating effects of market concentration and firm dominance on the service–satisfaction–performance relationship are examined. Our major finding is that market concentration dampens the relationship between customer satisfaction and airline profitability. Although the same moderating relationship was not found for market power, these results, combined, indicate that airlines can increase profits in concentrated markets without providing for the same, concomitant increases in customer satisfaction as airlines operating in more competitive markets. From a public policy perspective, our results point to the importance of regulators monitoring airline actions, such as mergers and alliances, that serve to increase the concentration of markets, but may result in lower levels of customer satisfaction.

A supply chain network design considering transportation cost discounts

Abstract: This study addresses an integrated facility location and inventory allocation problem considering transportation cost discounts. Specifically, this article considers two types of transportation discounts simultaneously: quantity discounts for inbound transportation cost and distance discounts for outbound transportation cost. This study uses an approximation procedure to simplify DC distance calculation details, and develops an algorithm to solve the aforementioned supply chain management (SCM) problems using nonlinear optimization techniques. Numerical studies illustrate the solution procedures and the effects of the model parameters on the SCM decisions and total costs. Results of this study serve as a reference for business managers and administrators.

Latent class nested logit model for analyzing high-speed rail access mode choice

Abstract: This paper explores access mode choice behavior, using a survey data collected in Taiwan. The latent class nested logit model is used to capture flexible substitution patterns among alternatives and preference heterogeneity across individuals while simultaneously identifying the number, sizes, and characteristics of market segments. The results indicate that a four-segment latent class nested logit model with individual characteristics in segment membership functions is the most preferred specification. Most high-speed rail travelers were cost-sensitive to access modes, and thus strategies that reduce the access costs can be more effective than reducing the access times.

Choosing a port: An analysis of containerized imports into the US

Abstract: Using a unique data set of individual shipments, port characteristics, and actual freight charges, we examined potential factors within management controls that affect the attractiveness of a port for containerized shipments. We hypothesized that the importance placed on each factor varies by the size of the shipper. We find support for our hypotheses that large shippers emphasize the factors affecting speed of delivery more than the freight charges compared to small shippers. These findings have managerial implications because investments in port development would pay off depending on the fit between the type of investment and the customers’ needs.

A location-inventory model for large three-level supply chains

Abstract: We study the location-inventory problem in three-level supply networks. Our model integrates three decisions: the distribution centers location, flows allocation, and shipment sizes. We propose a nonlinear continuous formulation, including transportation, fixed, handling and holding costs, which decomposes into a closed-form equation and a linear program when the DC flows are fixed. We thus develop an iterative heuristic that estimates the DC flows a priori, solves the linear program, and then improves the DC flow estimations. Extensive numerical experiments show that the approach can design large supply networks both effectively and efficiently, and a case study is discussed.

The dark side of logistics outsourcing – Unraveling the potential risks leading to failed relationships

Abstract: We identify and empirically examine the potential risk factors and their structural relationships that can cause a logistics outsourcing relationship to fail. Specifically, we investigate how the relationship risk as perceived by apparel wholesalers as user firms influence their evaluation on the asset and competence entrusted with their logistics service providers, which are logistics outsourcing risk factors considered important by the former in determining continued relationships with the latter. The results highlight the need for relationship management by user firms to mitigate the risks in asset and competence specifically invested in logistics service providers for their outsourced activities.

Stochastic optimization models for the airport gate assignment problem

Abstract: Uncertainties inherent in the airport traffic may lead to the unavailability of gates for accommodating scheduled flights. Incorporating random disruptions is crucial in constructing effective flight-gate assignments. We consider the gate assignment problem under uncertainty in flight arrival and departure times and develop stochastic programming models incorporating robustness measures based on the number of conflicting flights, idle and buffer times. The proposed models are formulated as large-scale mixed-integer programming problems and tabu search algorithms are implemented to obtain assignments of reasonable quality. We conduct a computational study to analyze the proposed alternate models and show the effectiveness of the solution methods.

The impact of flight delays on passenger demand and societal welfare

Abstract: US airline passengers increasingly have access to flight delay information from online sources. As a result, air passenger travel decisions can be expected to be influenced by delay information. In addition, delays affect airline operations, resulting in increased block times on routes and, in general, higher carrier costs and airfares. This paper examines the impact of flight delays on both passenger demand and airfares. Delays are calculated against scheduled block times as well as against more idealized feasible flight times. Based on econometric estimations, welfare impacts of flight delays are calculated. We find that flight delays on a route reduce passenger demand and raise airfares, producing significant decreases in both consumer and producer welfare. Since producer welfare effects are estimated to be three times as large as consumer welfare effects, we conclude that from an economic efficiency rationale, airlines should be required to pay for the bulk of flight delay remediation efforts.

Mergers and Acquisitions in Aviation – Management and Economic Perspectives on the Size of Airlines

Abstract: This paper reviews literature and management perspectives on airline mergers and acquisitions. We find that M&A/consolidation is seen as a “game-changer” and mandatory to survive in aviation markets. We, therefore, apply DEA models to 66 airlines to evaluate whether big is indeed always beautiful. Our results suggest that the optimal airline size is between 34 and 52 bn available seat kilometre capacity and that airlines with more than 200 bn ASK are definitely too large to operate efficiently. This also applies when revenues are included in the DEA models, which is central as yield management and ancillary revenues are increasingly important.

Dissecting preference heterogeneity in consumer stated choices

Abstract: This paper investigates alternative methods to account for preference heterogeneity in choice experiments. Heterogeneity can be explained by assuming its influence to impact the systematic component of utility, the stochastic one or both. Seven different models were estimated to search for heterogeneity along the three dimensions described. The comparison based on model performance and willingness to pay measures shows that methods to search for heterogeneity are not independent one from the other and might produce substantially different results giving rise to different policy implications.

Congestion, port expansion and spatial competition for US container imports

Abstract: The purpose of this paper is to analyze spatial competition, congestion and flows of container imports into the United States. An intermodal network flow model is developed and used to analyze congestion in the logistics system for container imports. The results indicate that congestion exists at most ports and its consequences are to raise costs at these nodes, and in some cases to divert traffic to other routes. Finally, if each of the ports expanded, the value of marginal capacity would converge to nil, and expansion would reduce congestion costs and waiting times.