Exact and heuristic methods to solve the berth allocation problem in bulk ports

In this paper, we study the dynamic hybrid berth allocation problem in bulk ports with the objective to minimize the total service times of the vessels. We propose two exact methods based on mixed integer programming and generalized set partitioning, and a heuristic method based on squeaky wheel optimization, explicitly considering the cargo type on the vessel. The formulations are compared through extensive numerical experiments based on instances inspired from real bulk port data. The results indicate that the set partitioning method and the heuristic method can be used to obtain near-optimal solutions for even larger problem size.     

A model of air cargo liberalization: passenger vs. all-cargo carriers

This paper employs a multi-market oligopoly model to examine the effect of cargo liberalization on competition between all-cargo carriers and mixed passenger/cargo carriers. We find that if home carriers engage in the joint production of cargo and passenger services, whereas foreign carriers produce the two outputs separately, then unilateral cargo liberalization by the home country will reduce home firm profits and increase foreign profits, and raise air fares for passenger travel when foreign competition in the passenger sector is limited. Our analysis suggests that the separation of air cargo and passenger rights might be fraught with difficulty in Asia due to the characteristics of its air cargo market, in which most passenger carriers have substantial cargo businesses and operate “combi” fleets.     

Optimal cargo container loading plans under stochastic demands for air express carriers

In this research, we develop a stochastic-demand cargo container loading plan model with the objective of minimizing the total operating cost, subject to the related operating constraints. The model is formulated as a nonlinear mixed integer program that is characterized as NP-hard. We employ a problem linearization technique, coupled with a mathematical programming solver, to develop a solution method. To preliminarily evaluate the model and the solution method, we perform a case study using data from an international air express carrier. The results show that the model and the solution method could be useful for air express carriers.     

Stochastic resource allocation for containerized cargo transportation networks when capacities are uncertain

We consider the stochastic resource allocation problem for containerized cargo transportation with uncertain capacities and network effects, in which a freight operator needs to allocate a certain amount of capacity to each product to maximize the expected profit. We formulate the problem as a constrained stochastic programming model and provide theoretical results that completely characterize the optimal solution to the model under a special case. Under a general case, we build an approximation model of the problem and propose a sampling based algorithm to solve the approximation model. A number of numerical experiments are offered to test the algorithm.     

Optimal solution for a cargo revenue management problem with allotment and spot arrivals

We consider a single-leg cargo revenue management problem, in which a two-dimensional cargo capacity is sold through allotment contracts and in the spot market. Capacity sold on an allotment basis is guaranteed. We optimally solve the problem of determining how much of the total weight and volume capacity to sell on an allotment basis, by deriving a closed-form expression of the objective function. We provide numerical examples of industry-size problems and perform sensitivity analysis by changing some problem parameters. The sensitivity analysis illustrates the dependency of the optimal decisions on the spot and allotment booking types. The remaining capacity is then sold over a booking horizon in the spot market. Allotment bookings and spot requests can arrive any time over the booking horizon. Since some of the allotment bookings might not show up at departure, cargo carriers tend to overbook the remaining capacity allocated to spot requests. For these requests, we formulate a discrete-time dynamic capacity control model, to decide which of the spot requests to accept, based on the total weight and volume of the allotment show-ups and spot bookings accepted at the time of an arrival. We solve the exact dynamic programming model for medium-size industry problems. Since the booking policy based on critical booking levels or time periods is not optimal, we propose several heuristics to solve large industry problems and derive an upper bound on the value function. We test their performance via simulation against the optimal solution, the upper bound, and the first-come first-served policy, and recommend a heuristic that performs well in a wide variety of numerical cases. Finally, we show via simulation, that our model outperforms the one existing in the literature, for small and medium-size industry problems.     

The ship routing and freight assignment problem for daily frequency operation of maritime liner shipping

To cope with excess capacity and improve service quality, maritime international liner carriers have recently adopted a new operational model known as daily frequency. In this new model, carriers provide daily pickup and delivery service to customers at major ports along the Pacific Rim. We investigate the ship routing and freight assignment problem for daily frequency operation of liner shipping. A solution procedure that incorporates a Lagrangian relaxation technique and local search was proposed. The numerical results show that Shanghai, Hong Kong and Singapore are ports that are ideal for carriers in establishing daily frequency operations along the Pacific Rim.     

Simultaneous optimization of schedule coordination and cargo allocation for liner container shipping networks

A liner container shipping carrier usually collects immediately-delivered goods that are produced by manufacturers in world factories, and transports the products to worldwide market destination by offering weekly shipping service. In practice, the carrier has to consider extra demurrage cost of containerized cargos incurred from waiting for weekly shipping service at ports. In this paper, we develop a mathematic programming model to maximize the carrier’s profitability by simultaneously optimizing the ship route scheduling and interrelated cargo allocation scheme. The nonlinear optimization model is transformed into an equivalent mixed-integer linear program, and its applicability is demonstrated by a case study.     

Evaluating competitiveness of air cargo express services

This paper explores the relative importance of factors that influence the adoption of air express delivery service, and evaluates the competitiveness of air cargo express carriers in the Korean market. Our AHP analysis shows that accuracy and promptness are the two most influential factors to competitiveness, and that DHL is most competitive in the Korean market, followed by FedEx, TNT, EMS, and UPS. We further examine both the factor importance and carriers’ competitiveness from the perspective of service users. While accuracy and promptness remain as important factors, price becomes the most important factor. Finally, an importance–performance analysis for each carrier is conduced, and managerial implications are drawn.     

Istanbul Airport (IGA) and quest of best competitive strategy for air cargo carriers in new competition environment: A fuzzy multi-criteria approach

Our paper determines the best competitive strategy that can be implemented by existing and potential air cargo carriers in the Turkish Air Cargo Industry with the operationalization of Istanbul Airport (IGA) and reveals the competitiveness level of the industry for four bases. We look at the competitiveness levels by analyzing the competitive environment of the industry nationally and internationally both before and post IGA (estimated). We use fuzzy TOPSIS (FTOPSIS) based on the Fuzzy AHP (FAHP) to handle vagueness, which is inherent in the nature of new competition conditions integrating the framework of Porter's five forces analysis. In our study, we use the five forces as our main criteria (with a total of 19 sub-criteria) and the competitive strategies as our alternatives. Our results reveal that the cost-focused strategy is the best competitive strategy that can be implemented by existing and potential carriers in the industry. Another significant result underscores the fact that IGA increases the competitiveness level of the Turkish Air Cargo Industry both nationally and internationally to a fairly high level. Also, the threat of potential competitors is first among the five forces in the industry's new conditions. Our study fills the gap in the literature on the effects of major structural changes in an air cargo industry on the competition among carriers.     

Optimal allocation of protective resources in urban rail transit networks against intentional attacks

This paper advances the field of network interdiction analysis by introducing an application to the urban rail transit network, deploying protective resources against intentional attacks. The resource allocation problem for urban rail transit systems is considered as a game between two players, the attacker interdicting certain rail stations to generate greatest disruption impact and the system defender fortifying the network to maximize the system’s robustness to external interdictions. This paper introduces a game-theoretic approach for enhancing urban transit networks’ robustness to intentional disruptions via optimally allocating protection resources. A tri-level defender–attacker–user game-theoretic model is developed to allocate protective resources among rail stations in the rail transit network. This paper is distinguished with previous studies in that more sophisticated interdiction behaviors by the attacker, such as coordinated attack on multiple locations and various attacking intensities, are specifically considered. Besides, a more complex multi-commodity network flow model is employed to model the commuter travel pattern in the degraded rail network after interdiction. An effective nested variable neighborhood search method is devised to obtain the solution to the game in an efficient manner. A case study based on the Singapore rail transit system and actual travel demand data is finally carried out to assess the protective resources’ effectiveness against intentional attacks.     

Towards a maturity model for big data analytics in airline network planning

The evaluation, acquisition and use of newly available big data sources has become a major strategic and organizational challenge for airline network planners. We address this challenge by developing a maturity model for big data readiness for airline network planning. The development of the maturity model is grounded in literature, expert interviews and case study research involving nine airlines. Four airline business models are represented, namely full-service carriers, low-cost airlines, scheduled charter airlines and cargo airlines. The maturity model has been well received with seven change requests in the model development phase. The revised version has been evaluated as exhaustive and useful by airline network planners. The self-assessment of airlines revealed low to medium maturity for most domains. Organizational factors show the lowest average maturity, IT architecture the highest. Full-service carriers seem to be more mature than airlines with different business models.     

Air cargo alliances and competition in passenger markets

This paper develops an oligopoly model to investigate the effect of an air cargo alliance on competition in passenger markets. We consider a model in which the partners, while continuing to offer their respective passenger services, jointly offer a new integrated cargo service by utilizing their passenger aircraft and routes. We find that such an alliance will likely increase the partners’ own outputs, while simultaneously decreasing its rivals’ outputs, in not only the cargo market but also the secondary passenger market. Furthermore, the alliance is likely to reduce passenger prices and increase total surplus.     

Traveler satisfaction in rapid rail systems: The case of Istanbul metro

Multifaceted characteristics of urban travel have an impact on the passengers' overall satisfaction with the transport system. In this study, we investigate the interrelationships among traveler satisfaction, travel and traveler characteristics, and service performance in a multimodal network that comprises of a trunk line and its feeder lines. We analyze the factors influencing the choices of access to rail transit stations and the satisfaction of transit travelers with the rapid rail transit systems. We quantitatively study these relationships and demonstrate the complexity of evaluating transit service performance. Since the interrelationships among variables affecting this system are mainly stochastic, we analyze the satisfaction with transit system problem using a Bayesian Belief Network (BBN), which helps capture the causality among variables with inherent uncertainty. Using the case of Istanbul, we employ the BBN as a decision support tool for policy-makers to analyze the rapid rail transit services and determine policies for improving the quality and the level of service to increase the satisfaction with transit system. In the case study, satisfaction with accessibility and access mode variables are found to be more effective variables than total travel time for travel time satisfaction, confirming the significant role of access in multimodal travels.     

Towards a taxonomy-based preferred-customer model for suppliers in air cargo express service markets

Drawing on social exchange and push–pull–mooring theories, this paper develops a taxonomy-based preferred-customer model for B2B air express markets. Our model extends the conventional bilateral customer-supplier relationship perspective of customer portfolio management to include competition effects for more comprehensive (trilateral) strategic decision making. Based on this unified framework, our a survey of 180 customers of air cargo express carriers identifies three distinctive groups of preferred customers. In addition to the effect of competitors on air express carriers’ prioritization of customers, which is further complicated by a satisfaction paradox and spurious loyalty, we further establish classification indicators for differentiating preferred from non-preferred customers. Notably, although commonly used in practice, we find sales volumes to be ineffective for that purpose.     

Recovery of disruptions in rapid transit networks

This paper studies the disruption management problem of rapid transit rail networks. Besides optimizing the timetable and the rolling stock schedules, we explicitly deal with the effects of the disruption on the passenger demand.We propose a two-step approach that combines an integrated optimization model (for the timetable and rolling stock) with a model for the passengers’ behavior.We report our computational tests on realistic problem instances of the Spanish rail operator RENFE. The proposed approach is able to find solutions with a very good balance between various managerial goals within a few minutes.     

Issues on liberalization of air cargo services in international aviation

This paper provides a general discussion of various issues related to the liberalization of air cargo services in international aviation. It shows that all-cargo carriers may have different routing needs than passenger carriers and thus require different sets of air traffic rights from those needed by passenger carriers. On the other hand, separation of air cargo and passenger rights will be fraught with difficulty in Asia because of distinctive characteristics of its air cargo market, where most passenger carriers have substantial cargo business and operate “combi” fleets. Customs and inter-modal transportation are also discussed in the context of cargo liberalization.     

Exploring the impacts of land use by service coverage and station-level accessibility on rail transit ridership

In this study, we employ spatial regression analysis to empirically investigate the impacts of land use, rail service coverage, and rail station accessibility on rail transit ridership in the city of Seoul and the surrounding metropolitan region. Our analyses suggest that a rail transit service coverage boundary of 500 m provides the best fit for estimating rail transit ridership levels. With regard to land use, our results confirm that density is positively related to rail transit ridership within a 750 m radius of each station. In contrast, land use diversity is not associated with rail transit ridership. We also found that station-level accessibility is as important as land use for explaining rail transit ridership levels. Finally, we conclude that development density and station-level accessibility measures such as the number of station entrances or exits and the number of bus routes at the station are the most important and consistent factors for promoting rail transit ridership.     

Responses of air cargo carriers to industrial changes

This study examines how product characteristics, values, inventory cost, shipping charges, shipping distance, and time affect an international firm's choice of air carrier. An individual choice model is constructed by assuming that the shipper in a specific industry chooses the optimal air cargo carrier with the minimal logistics cost. The study further aggregates air cargo demands on different routes for the carriers by considering the spatial distribution of the origin-destination pattern and any temporal changes in the industrial structure. A case study is used to illustrate the application of the proposed model using data from Taiwan Taoyuan International Airport and the industrial economics database in Taiwan. The results show that shippers with high product value and short delivery distance focus on the shipping charge and prefer choosing the air cargo carrier that offers more flights. Further a carrier may achieve a larger market share if its supply attributes match the industrial structure and the product characteristics of the market on the route. Finally, because dynamic changes in the industrial structure and product value have been captured, the results are more accurate than that from the Grey model.     

Moving freight on public transit: Best practices,challenges, and opportunities

Freight on Transit (FOT) refers to an operational strategy where public transit vehicles and/or infrastructure are used to move freight. Examples include moving goods alongside passengers on buses, attaching cargo trailers to transit vehicles, and operating freight vehicles between trains on subway lines. This paper describes the methods and results of a three-round Delphi study engaging 34 transportation experts to explore challenges and opportunities of FOT and to conceptualize and evaluate potential FOT operations in Toronto. Traditional Delphi methods were used for the exploration of FOT challenges and opportunities, and a modified approach was formulated to integrate experts' opinions and develop new FOT concepts for Toronto. The results support previous claims that technical challenges of FOT may be easier to overcome than institutional barriers. Evaluation of potential FOT operating strategies in Toronto suggests that while the current public transit network does not have capacity to support additional movements, there may be realistic opportunities to include freight service in future projects as a means of offsetting operating costs and reducing the impacts of goods movements.     

Do low cost carriers have different corporate governance models?

In this paper, we investigate whether different business models in the same industry (passenger air transportation) lead to different corporate governance models. We found that low-cost carriers organise their boards differently from full service carriers to achieve lower costs and a faster decision-making process that is required by their business model. We also found that low-cost carriers and full service carriers solve their potential agency cost problems differently and that full service carriers have more board monitoring committees, and low-cost carriers have a closer coincidence of interests between shareholders and executive directors.