Liner hub-and-spoke shipping network design

This paper proposes a liner hub-and-spoke shipping network design problem by introducing the concept of a main port, as well as some container shipping constraints such as multi-type container shipment and transit time constraints, which are seldom considered in the previous studies. It develops a mixed-integer programming model with nonconvex multi-linear terms for the proposed problem. An efficient genetic algorithm embedded with a multi-stage decomposition approach is developed to solve the model. Numerical experiments are carried out to assess the effectiveness of the proposed model and the efficiency of the proposed algorithm.     

Liner shipping hub network design in a competitive environment

A mixed integer programming formulation is proposed for hub-and-spoke network design in a competitive environment. It addresses the competition between a newcomer liner service provider and an existing dominating operator, both operating on hub-and-spoke networks. The newcomer company maximizes its market share—which depends on the service time and transportation cost—by locating a predefined number of hubs at candidate ports and designing its network. While general-purpose solvers do not solve instances of even small size, an accelerated Lagrangian method combined with a primal heuristic obtains promising bounds. Our computational experiments on real instances of practical size indicate superiority of our approach.     

The multistage stochastic integer load planning problem

Time-definite freight delivery common carriers, who pickup, consolidate and deliver small shipments are a key third-party logistics service provider in the supply chains. Under uncertain demands, carrier’s multistage stochastic integer load planning in the pure hub-and-spoke line-haul operations network is to determine multistage freight paths and distribute trailers over time while meeting operational restrictions, service requirements, and balancing trailer inventory at the termination of planning horizon. We developed a heuristic approach, scenario aggregation with embedded branching on the binary variables. The numerical experiments showed a proactive operations strategy with a lower operating cost than the conventionally deterministic approach.     

How do carriers price connecting flights? Evidence from intercontinental flights from Europe

In civil aviation, hub-and-spoke (HS) networks are used by all large carriers. The importance of this system implies that many travelers use connecting flights. Nevertheless, only scarce knowledge is available on price formation of these trips. In this paper, we focus on the fares of connecting intercontinental flights, with one stop and at least one competing direct flight. We develop a simple model of a HS network, with imperfect substitutability between direct and indirect flights and Cournot competition on every route in the network. We test the model empirically, using reported fares for flights from seven European origins, including the five major airports in Europe, to five non-European destinations. We find that the fare of a connecting flight can be expressed as the weighted average of the fare of its direct competitor, the travel times of both flights its costs and the monetary value of the utility attached to the trip. The weight of the direct fare decreases as product diversity increases.     

Optimization of postal express line network under mixed driving pattern of trucks

Details about the movement of trucks on postal express lines are investigated to improve the performances of mail distribution. A mixed driving pattern of trucks is introduced to minimize the transportation cost of a postal express line network with a service level requirement. We formulate this problem as a mixed p meeting depots location with shipment scheduling problem and build a MINLP model. A two-level tabu search procedure based on shipment grouping method is developed. Through a series of computational experiments and sensitivity analysis on different instances, some managerial insights of the network under mixed driving pattern are revealed.     

发展中枢辐射铁路物流的探讨

传统的铁路物流组织模式有其局限性,已难以满足市场对快速运输的需求,铁路企业的改革势在必行。在阐述中枢辐射铁路物流表现形式的基础上,分析铁路企业发展中枢辐射铁路物流的必要性和可行性及所面临的困难,同时就铁路企业如何发展中枢辐射铁路物流提出了建设性意见。     

A supply chain network design model for biomass co-firing in coal-fired power plants

We propose a framework for designing the supply chain network for biomass co-firing in coal-fired power plants. This framework is inspired by existing practices with products with similar physical characteristics to biomass. We present a hub-and-spoke supply chain network design model for long-haul delivery of biomass. This model is a mixed integer linear program solved using benders decomposition algorithm. Numerical analysis indicates that 100 million tons of biomass are located within 75 miles from a coal plant and could be delivered at $8.53/dry-ton; 60 million tons of biomass are located beyond 75 miles and could be delivered at $36/dry-ton.     

Planning and optimization of intermodal hub-and-spoke network under mixed uncertainty

This paper addresses the planning and optimization of intermodal hub-and-spoke (IH&S) network considering mixed uncertainties in both transportation cost and travel time. Different from previous studies, this paper develops a novel modeling framework for the IH&S network design problem to jointly minimize the expected value of total transportation costs and the maximum travel time requirement in term of critical value. A new hybrid methodology by combining fuzzy random simulation (FRS) technique and multi-start simulated annealing (MSA) algorithm is designed to solve the proposed model. Numerical experiments are implemented to verify the effectiveness of the proposed model and solution approach.     

A note on the competitive advantage of large hub-and-spoke networks

This note explores the extent to which airlines operating large hub-and-spoke networks secure a competitive advantage. More specifically, this paper explores the intricate relationship which arises among productive efficiencies and profitability when the size of the hub-and-spoke network expands. To this end, Brueckner and Spiller (1991, International Journal of Industrial Organization 9, 323–342) airline economics model is generalized by allowing the size of the hub-and-spoke network to vary. The central result shows that, although the model exhibits decreasing returns to firm/network size (RTNS), nonetheless there is a competitive advantage to increasing the size of a network.     

Airline network structure under demand uncertainty

In this paper, we provide another reason that may explain the adoption of the hub-and-spoke network structure in the airline industry. We show that when an airline has to decide on its capacity before the demand conditions are perfectly known, a hub-and-spoke (h&s) network structure by pooling passengers from several markets into the same plane helps the firm to lower its cost of excess capacity in the case of low demand and to improve its capacity allocation in the case of high demand.     

Debunking some common myths about airport hubs

Much of the passenger air transportation market is served through hub-and-spoke operations with traffic being funneled through a number of major airports. This system has come under attack as protective of the airlines that center their operations on large hubs and is often as result, seen as not serving the public interest. This paper looks at some of the arguments that have been laid against the hub-and-spoke system. It does not offer a balanced perspective in that there are many problems with the system that are not touched upon here, but rather it seeks to question some of the economic logic that has been used to attack the hub-and-spoke structure. While the issues extend to many air transportation markets, the focus here is primarily on the US domestic situation.PrologueThe impacts of the events of September 11, combined with the move into economic recession in the US that was already underway at that time, have led to serious financial difficulties for many of the World's airlines. Some, such as Midway in the US, immediately sought bankruptcy protection whilst others, such as Sabena and Swissair in Europe, took a little longer to fade away. Most of those that remain, despite combinations of financial assistance, have been struggling in the current economic climate.The subject addressed here is not directly concerned with this issue, although there are important overlapping longer-term linkages. Rather it looks at the structure of the airline networks that dominate the provision of air services. These structures still remain, although there are inevitable changes occurring. This paper was initially drafted prior to the recent changes that have taken place in air transportation markets. It retains much of the original material that was presented at the Amsterdam meeting, with some minor up-dating. The theme may seem less important now than at the time of the meeting, but this, I would argue, is perhaps a premature view. The combination of derived demand, relatively easy market entry, lumpiness in investments, etc., have resulted over time in dramatic changes in the fortunes of the sector and individual actors in it. There are, though, a number of recurring themes that pose interesting questions for the applied economist and one of these is the nature of efficient networks.     

Network structure and capacity requirement: The case of China

This paper analyzes capacity requirement by alternative network structures. Based on a simple model, it is concluded that the capacity required under a hub-and-spoke network would be more than twice as large as the capacity required under a fully connected network. In recent years, China has experienced unprecedented growth in the demand for air travel, which has put continuous pressure on the expansion in airport capacity. Still as a developing country, China suffers from insufficient investment in infrastructure. Therefore, given scarce capacity, it may be more efficient for the major air carriers not to adopt the hub-and-spoke network in Chinese domestic markets.     

Hub-and-spoke network design for container shipping along the Yangtze River

Increasingly large, high-tonnage containerships are becoming a common sight on the Yangtze River, and the shipping network is being transformed accordingly. This paper reports the design of a hub-and-spoke network for a shipping company that is consistent with the characteristics of the Yangtze River. We first explore the economies of scale for container shipping by applying empirical data. Next, we propose a mixed-integer linear programming model, factoring in ship-operating and container-handling costs. We then conduct a numerical experiment and test the effectiveness of the model, and finally discuss the implications of hub-and-spoke shipping network design. The findings reported herein support the trends toward cargo concentration and port regionalization along the Yangtze River.     

High-technology employment and hub airports

Deregulation of the US domestic air transport market in 1978 brought significant benefits to air travelers. The scheduled airlines have been given the freedom to improve their efficiency through being able to adopt efficient network strategies and more effective operating practices. This study examines empirically the advantages enjoyed by those passengers having access to a major hub airport. These often include more direct services, more frequent services and a wider range of interconnecting destinations. We seek to examine the benefits that local urban areas enjoy as the result of a major airline selecting the region as the fulcrum point for its hub-and-spoke services.     

Price planning for time-definite less-than-truckload freight services

Price planning simultaneous determines the service demand (with associated prices) and an operational plan to maximize a carrier’s profit. We modeled this integral-constrained concave program in the link formulation and proposed an implicit enumeration embedded with Lagrangian Relaxation upper bounds to determine the optimal prices. Computations on Taiwan’s time-definite less-than-truckload freight market showed that the carrier needs to simultaneously re-evaluate its network capacity while determining prices. The common practice of distance-based pricing that sets price by a base rate over direct shipment distance underestimates operating cost, specifically operating losses for short distance shipments.     

An integrated model for stock replenishment and shipment scheduling under common carrier dispatch costs

We examine a joint inventory replenishment and shipment scheduling problem that arises in the context of a vendor-managed inventory (VMI) arrangement. Since a temporal shipment consolidation policy is being implemented, the inventory requirements at the vendor are affected by the timing and quantity of shipment release. The vendor’s problem is to determine an integrated policy for inventory replenishment and shipment release and to set its parameters. We develop analytical models for computing such integrated policies where it is economical to use common carriage for outbound transportation. We propose algorithmic approaches to set the optimal policy parameter values.     

Analysis of prospective airline mergers using a simulated annealing model

This paper examines the efficacy of a simulated annealing model of the US airline network in analyzing potential mergers between major airlines. The simulation performs satisfactorily in modeling the current hub-and-spoke system focusing on the effects on passenger routings, producer profits, and consumer welfare. In general, the simulated annealing model reasonably demonstrates the price and demand effects due to a merger of major carriers. While it cannot take into account all relevant information, such as labor union relationships and negotiating tactics, it can offers insight into the implications of airline mergers.     

Elasticities of mode choice probabilities and market elasticities of demand: Evidence from a simultaneous mode choice/shipment-size freight transport model

This paper presents empirical estimates of market elasticities of demand and elasticities of mode choice probabilities in the intercity freight transport market. Results are derived from a mixed discrete/continuous choice model of mode and shipment size. The mode choice component of the full model was specified as a binary probit function. The two modes considered were rail and regulated common carriers (full truck load). Data was drawn from the US Commodity Transportation Survey consisting of individual shipments of manufactured goods identified at the most disaggregate level. Results obtained in this study are compared with those obtained in previous studies, and areas of similarities and dissimilarities in the magnitude as well as interpretation of the results are highlighted. The own-price and cross-price elasticities of mode choice probabilities were found to vary from 1.44 to 1.88, and from 1.54 to 1.75, respectively. The market price elasticities of demand were found to vary significantly across commodity groups and geographic territories. Among the 40 market segments considered, the truck price elasticity of demand ranged between −0.749 and −2.525; the rail price elasticity of demand was slightly larger, ranging between −0.956 and −2.489; and the rail–truck cross-price elasticity of demand ranged between 0.904 and 2.532.     

Integration of inventory and transportation decisions in a logistics system

This paper addresses some of the challenges faced by a company which is responsible for delivering coal to its four subsidiaries situated along a river, through river hired or self-owned vessels. We propose to adopt a vendor managed inventory concept that involves establishment of a central warehouse at the port, and apply the Markov Decision Process (MDP) to formulate both ordering and delivery problems, considering different transportation modes, costs, and inventory issues. An efficient algorithm is developed for solving the MDP models. Our computational tests show that the proposed strategy can significantly reduce the overall system costs while maintaining smooth Just-in-Time supplies of coal to the subsidiaries.     

Airline mergers and their effect on network structure

The Airline Deregulation Act of 1978 introduced high-level competition into the US domestic industry. The resulting network changes have created a deluge of research, largely focused on the hub-and-spoke structure. Over 15 years have passed since deregulation, and the industry still appears somewhat unsettled. Recent concerns of domestic carriers include downsizing of some hubs, and discussions of further consolidation of operations. Mergers may be the answer for airlines with shrinking markets within the US transportation system. This study examines the effect on network structure created by the merger of two carriers from the perspective of hub structures, accessibility and geographic coverage.