A heuristic approach for solving an integrated gate reassignment and taxi scheduling problem

Capacity limitation of airport ground operation is one of the major limiting factors in air traffic operation. The congestion on the gate and taxiway causes severe delay and propagate effect on the flight schedule. This paper considers the problem of integrated gate reassignment and taxiway scheduling, in which complex constraints related to runway restriction, gate allocation and taxiway conflict are all incorporated when determining the schedule. To solve this problem, we propose a novel heuristic approach. First, all possible aircraft schedules are enumerated by disretizing the waiting time along the path. Then, the cost is evaluated for each schedule and the conflict detection is conducted to generate constraint sets. Finally, we propose a set partition model, in which each decision variable denotes a candidate schedule that takes into account the possible constraints when generated. This method is compared with a sequential method that solves gate reassignment and taxiway scheduling problem separately. Computational results highlight the strength of our method.     

Modeling green vehicle adoption: An integrated approach for policy evaluation

This article employs an integrated discrete-continuous car ownership model to jointly forecast households’ future preferences on vehicle type, quantity and use, and to estimate greenhouse gas (GHG) emissions. The model system is estimated on a dataset collected from a web-based stated preference survey conducted in Maryland in 2014. The data contain vehicle purchase decisions and sociodemographic information of 456 households who were requested to state their future preferences over a 9-year period (2014–2022). In each time period, a respondent is faced to four alternatives that include the current vehicle, a new gasoline vehicle, a new hybrid electric vehicle, and a new battery electric vehicle. Intertemporal choices between conventional and “green” vehicles such as hybrid and electric cars capture dynamics in vehicle purchase decisions. Short run and medium-long run situations were predicted and compared based on the first 4-year data and the entire 9-year data of the dynamic panel. Vehicle GHG emissions were calculated correspondingly. We find the introduction of “green” vehicles makes a positive impact on car ownership and use, especially in a medium-long run. Two “green” taxation policies, gasoline tax and ownership tax, were proposed and their impact on vehicle use and emission reductions was evaluated. Results indicate that: (a) gasoline tax is a more effective way to reduce vehicle miles traveled and GHG emissions and (b) gasoline tax makes a higher impact on car use and emission reductions in the medium-long run, while ownership tax makes a higher impact in the short run.     

Potential effects of ICT on face-to-face meeting opportunities: a GIS-based time-geographic approach

People in modern societies are increasingly experiencing the impacts of information and communication technologies (ICT) on their daily activities and their interactions with other people. These changing activity and interaction patterns due to the use of ICT have important implications to human activity and travel patterns. There are scant studies offering a spatiotemporal analytical framework that can help researchers examine the interactions between ICT and human activities at the individual level. Time geography offers a useful approach of studying individual activities and human interactions in a space-and-time context. By extending a time-geographic analytical framework, this study uses an example of arranging a face-to-face (F2F) meeting between two people to illustrate how potential F2F meeting opportunities can be impacted under four different scenarios of phone access levels. This spatiotemporal analytical framework and the various phone access scenarios are implemented in a space-time geographic information system (GIS) to demonstrate the feasibility of this analytical framework. In addition, this time-geographic framework offers analysis functions in support of quantitative assessments of ICT’s impacts on human activities.     

Decomposition approach for integrated intermodal logistics network design

The integrated intermodal logistics network design problem consists of determining terminal locations and selecting regular routes and transportation modes for loads. This problem was formulated using a path-based formulation and a decomposition-based search algorithm has been proposed for its solution. Computational results show that this approach is able to obtain optimal solutions for non-trivial problem instances of up to 150 nodes in reasonable computational times. Previous studies have only been able to obtain approximate solutions for network problems of this size. A few general insights about the effects of design parameters on solution characteristics were also obtained.     

Life-cycle CO2 emissions and influential factors for asphalt highway construction and maintenance activities in China

This study tried to clarify the magnitude of CO₂ emissions from highway construction and maintenance in China through life cycle assessment (LCA) method. For this, 227 real highway projects constructed from the year 2000 to 2011 in Zhejiang Province, China are classified into six types by two categories of N road (62 projects without grand bridge, great bridge and tunnel) and Y road (165 projects with the same road structures) and three sub-categories of (i) newly constructed road, (ii) replacing pavement road and (iii) full rehabilitated road. Significant influential factors of LCA results were revealed through multivariate linear regression models, combined with data quality assessment and sensitivity analysis. Numerical interval of assessment results indicate that the construction emissions of N highway project are more centralized to no more than 2900 t/lane-km, while Y project have a normal upper boundary of construction CO₂ emissions, about 5000 t/lane-km. The contribution of maintenance to CO₂ emissions probably could exceed that of newly construction both for Y project and N project. In addition, the pavement replacing and rehabilitation could bring about large amount of CO₂ emissions which even match with the CO₂ emissions from cumulative traffic volume during highway's life cycle. There are common factors for six categories. Cement and steel are the top largest CO₂ emissions contributors and sensitive factors for N road and Y road. The LCA results are not sensitive to the local construction materials but sensitive to the emission factor of diesel used in transportation and on-site construction.     

A GIS-based Bayesian approach for analyzing spatial–temporal patterns of intra-city motor vehicle crashes

This paper develops a GIS-based Bayesian approach for intra-city motor vehicle crash analysis. Five-year crash data for Harris County (primarily the City of Houston), Texas are analyzed using a geographic information system (GIS), and spatial–temporal patterns of relative crash risks are identified based on a Bayesian approach. This approach is used to identify and rank roadway segments with potentially high risks for crashes so that preventive actions can be taken to reduce the risks in these segments. Results demonstrate the approach is useful in estimating the relative crash risks, eliminating the instability of estimates while maintaining overall safety trends. The 3-D posterior risk maps show risky roadway segments where safety improvements need to be implemented. Results of GIS-based Bayesian mapping are also useful for travelers to choose relatively safer routes.     

Reducing the wasted transportation capacity of Personal Rapid Transit systems: An integrated model and multi-objective optimization approach

This study addresses the problem of wasted transportation capacity in Personal Rapid Transit (PRT) systems. We propose a two-tier transportation model that integrates PRT and capillary transportation systems. We study a related multi-objective empty vehicle redistribution problem that attempts to minimize empty movement and the number of vehicles used. Furthermore, we design a hybrid multi-objective genetic algorithm that integrates multiple crossover operators and linear programming techniques to solve the proposed problem. Evaluations indicate that our algorithm produces satisfactory results, and simulations confirm the efficiency of our proposed two-tier transportation system.     

Tourism in Nepal: post-monarchy challenges

Monarchy has remained a stimulus in the touristic representation of Nepal. Recent political changes in Nepal abolished the traditional monarchy and declared Nepal a Federal Democratic Republic. Since Nepal's national identity was closely intertwined with the Hindu religion and monarchy, their absence indicates a reason sound enough to bring about a change in the traditional representation of Nepal in tourism. This paper first contextualises the role of monarchy in Nepalese tourism. It then looks into the challenges perceived by the tourism industry arising from the absence of the institution of monarchy. Data collected through interviews and questionnaires from the industry representatives and other library-based resources show that the biggest challenge ahead would be to the future of Nepal's existing tourism imagery. This is because, first, monarchy has a role in projecting Nepal as an exotic and mystic destination. Second, because the urge to diversify Nepal's tourism activities due to the increased quest for newly emerging regionalism means the traditional representations in tourism would not remain uncontested. These results lead us to a conclusion that the stereotypical image of tourism tends to be challenged in a new cultural climate brought about by a major change in the political regime.     

An integrated performance evaluation approach for the Indian international airports

This paper deals with the applications of best worst method (BWM) and multi-attributive border approximation area comparison (MABAC) method to assess the performance of 32 major Indian international airports based on eight evaluation criteria. The BWM is applied to derive the criteria weights based on the opinions of four decision makers, while MABAC method is employed to rank the considered airports from the best to the worst along with the identification of their relative strengths and weaknesses. The advantages of these methodologies are also enumerated. It is observed that annual revenue is the most important evaluation criterion, followed by the total number of passengers. Based on this integrated analysis, Indira Gandhi International Airport and Surat International Airport respectively emerge out as the best and the worst performing international airports in India.     

A dynamic approach for aircraft assignment and maintenance scheduling by airlines

The problems of assigning planes to flights and of fleet maintenance operations scheduling are considered in this paper. While recent approaches make use of artificial intelligence techniques running on main frame computers to solve combinatorial optimization problems for nominal operations, a dynamic approach is proposed here to face on-line operation conditions. The proposed solution mixes a Dynamic Programming approach (to cope with the fleet assignment problem) and a heuristic technique (to solve the embedded maintenance schedule problem). When applied to a medium charter airline, this approach shows acceptability characteristics for operational staffs, while providing efficient solutions. The proposed solution scheme can be considered as the basis for the development of an on-line decision support system for fleet operations management within airlines.     

Optimal transportation and business cycles in an integrated production-inventory model with a discrete credit period

This paper considers the impact of discrete trade-credit policy depending on the purchased quantity of raw-materials on an integrated multi-cycle production inventory system of a raw-material supplier and a manufacturer in some business cycles during finite time horizon. The manufacturer collects raw-materials with offer of free transportation cost in some transportation cycles. Our objective is to get the optimal number of transportation and business cycles in two models with three cases depending on different position of the credit period with respect to production period and cycle length. Some numerical examples have been illustrated along with sensitivity analysis and managerial insights.     

A method for assessing highway qualities to integrate values in highway planning

Highway infrastructure planning is most often oriented toward assessing and maintaining physical inventories but it is often the lack of social knowledge about how people perceive, value and use a transportation system that generates the greatest user conflict and mistrust of public agency behavior. Using results from a 2001 statewide survey of Alaska residents, this paper presents a methodology for examining highway systems as a collection of intrinsic highway qualities and special places that provide a spectrum of highway experience opportunities. The concept of a highway experience opportunity spectrum is described and a number of potential dimensions for creating experience opportunity classes are suggested. With knowledge of spatial locations of intrinsic highway qualities, transportation planners can make informed choices to maintain or alter the set of highway experience opportunities associated with a highway system.     

Determinants of performance for agritourism farms: an alternative approach

Previous studies on determinants of agritourism farm performance are inconclusive. Moreover, the key success factors of high and low performance may differ. Differing from previous studies, this study applies quantile regression to identify the determinants of agritourism farm performance in different categories based on Taiwanese agritourism farms census data. The results indicate that large farms perform well for those in the high-performance categories. The quantity and quality of human resources are key success factors for mid- and high-performance farms. Additionally, agritourism business model generally plays a critical role in determining performance.     

A GIS-based spatial statistical approach to modeling job accessibility by transportation mode: case study of Columbus,Ohio

Improving job accessibility based on transport connectivity helps to address equity issues. Spatial autocorrelation (SA) is also a focus of interest in transportation planning, but has been neglected in analyzing job accessibility in metropolitan areas. In this study, GIS-based job accessibilities by walking, transit, and car are computed for the metropolitan area of Columbus, Ohio, and three transport-based spatial autoregressive (SAR) models are estimated to account for the SA of job accessibility among neighboring block groups, while controlling for built-environment and socioeconomic factors. SA intensities and extents are compared in order to better understand local spatial clusters of job accessibility across the region. Direct and indirect spillover effects due to an investment change in transportation facilities are estimated and provide important transportation planning information. The results also show that walking-accessed jobs are primarily related to physical settings (e.g., land uses) at the local level. Locations with a higher share of zero-vehicle housing units have better job accessibility by transit. There is a spatial mismatch between Asian population clusters and transit-accessed jobs, possibly because of the car-oriented residential clusters around Honda of America Manufacturing in suburban areas. More importantly, locations with a higher share of single-parent households are at a disadvantage in overall job accessibility. Due to its complex transportation needs, a society friendly to single parents should spatially integrate accessible jobs with other needed activities via land-use and transportation planning. Alternatively, car-ownership programs and non-spatial social supports also might be effective to help secure job opportunities and perform daily life activities.     

A GIS-based time-geographic approach of studying individual activities and interactions in a hybrid physical–virtual space

Modern information and communication technologies (ICT) are changing human activity and travel patterns that could have significant implications to our everyday lives and the human organization of space. Time geography, which examines human activities under various constraints in a space–time context, provides a useful framework to analyze the complex spatio-temporal relationships among activities and interactions taking place in both physical and virtual spaces. However, virtual activities and interactions conducted via ICT have characteristics that cannot be properly represented and analyzed under the classical time-geographic framework. This paper extends classical time-geographic concepts to accommodate the needs of representing and analyzing all activities and interactions in a hybrid physical–virtual space. In addition, this paper presents a space–time geographic information system (GIS) design that is capable of organizing complex activity and interaction data as spatio-temporal processes in an integrated space–time environment. This space–time GIS design offers a useful analytical environment for researchers to study increasingly dynamic human activity and travel patterns in today’s society and their implications toward changing travel demand patterns from both spatial and temporal perspectives.     

Locating manufacturing and distribution centers: An integrated supply chain-based spatial interaction approach

This study investigates the facility location problem of transnational personal computer (PC) manufacturing for the domestic market of China. An integrated supply chain-based spatial interaction model is formulated to determine facility locations of the transnational PC manufacturing centers and regional product distribution centers in China, with the goal of maximizing the potential rate of return on facility investment. The numerical results show that the Shanghai municipality is ranked highest for siting both the manufacturing and distribution centers for a transnational PC manufacturing enterprise.     

Assessing policy measures for the stimulation of intermodal transport: a GIS-based policy analysis

Intermodal transport is the combination and integration of several transport modes (such as rail, inland waterways with road transport). In order to make the transhipment easy and efficient standard loading units are used, such as containers or swap-bodies. As for the main haul, more environmental friendly modes are used (rail and inland waterways) and a modal shift towards these modes can help in reducing the congestion. Therefore several policies are directed to stimulate the intermodal transport market.In this paper, a location analysis model for Belgian intermodal terminals (LAMBIT) is developed and used to assess different policy measures in Belgium. The simulations show that the different policy measures oriented towards the rail/road and inland waterways/road combinations should be incorporated in a coherent, integrated vision, in order to not create a modal shift between the different intermodal transport options. The methodology can easily be extended towards a European scale.     

Aircraft routing for on-demand air transportation with service upgrade and maintenance events: Compact model and case study

This paper addresses a problem faced by airline companies that offer on-demand flight services. Given a list of flight requests, the company has to assign its aircraft to these requests while minimizing operational costs. The main issue in this planning process involves the positioning of aircraft when they are not available at the airports of customer departure. The cost of this positioning should be as low as possible, as the customers’ expenditures are proportional to the requested flight hours only. We propose a compact optimization model to support decision making in this situation. It takes into account the mandatory aircraft maintenance events and the possibility of flight upgrades according to the their impact on the operational costs. One important and novel feature of this model is that it allows the anticipation or postponement of the beginning of flights and maintenance events within a given tolerance, giving more freedom to the decision making process. This research is motivated by a case study carried out with a fractional management airline company that operates in European and Asian countries. Computational experiments using real-life data collected from the company show that the proposed model can be solved quickly using general-purpose optimization software, including open-source alternatives. The results indicate that the obtained solutions lead to significant reductions in the operational costs and hence can be used in practice for effective decision making.     

Flows into tourist areas: an econometric approach

The globalisation of the tourism industry has led to a horizontal and vertical penetration of firms, leading to strong competition in all tourist centres. In light of these circumstances there is a need to develop strategies that encourage entrepreneurial actions and help firms to design the most competitive tourism offer possible. For the development of these strategies, the current work attempts to identify the degree of interrelation existing between the different tourist markets. Specifically, the study is based on an analysis of the evolution in the relations between the main tourist‐receiving centres in Spain. It identifies the short‐ and long‐term dynamic relations existing between them, and determines their degree of interdependence and any potential leadership relations between them. The methodology used is the one underlying Cointegration theory and vector autoregressive theory, together with forecast error variance decomposition and the impulse‐response function. Copyright © 2008 John Wiley & Sons, Ltd.