Yu Hern Chang

Fuzzy multicriteria analysis for performance evaluation of bus companies

Abstract This paper presents an effective fuzzy multicriteria analysis (MA) approach to performance evaluation for urban public transport systems involving multiple criteria of multilevel hierarchies and subjective assessments of decision alternatives. The subjectiveness and imprecision of the evaluation process are modeled as fuzzy numbers by means of linguistic terms. To avoid the complex and unreliable comparison of fuzzy numbers, typically required by fuzzy MA models, the concept of the degree of optimality of each alternative with respect to each criterion is used to transform a weighted fuzzy performance matrix into a fuzzy singleton matrix. Incorporated with the decision maker’s attitude towards risk, a crisp overall performance index is obtained for each alternative based on the concept of the ideal solution. The approach presented is computationally efficient, and its underlying concepts are simple and comprehensible. A case study on 10 bus companies of an urban public transport system in Taiwan is conducted to illustrate the effectiveness of the approach.

Modeling subjective evaluation for fuzzy group multicriteria decision making

This paper presents a new fuzzy multicriteria decision making (MCDM) approach for evaluating decision alternatives involving subjective judgements made by a group of decision makers. A pairwise comparison process is used to help individual decision makers make comparative judgements, and a linguistic rating method is used for making absolute judgements. A hierarchical weighting method is developed to assess the weights of a large number of evaluation criteria by pairwise comparisons. To reflect the inherent imprecision of subjective judgements, individual assessments are aggregated as a group assessment using triangular fuzzy numbers. To obtain a cardinal preference value for each decision alternative, a new fuzzy MCDM algorithm is developed by extending the concept of the degree of optimality to incorporate criteria weights in the distance measurement. An empirical study of aircraft selection is presented to illustrate the effectiveness of the approach.

A multiobjective model for passenger train services planning: application to Taiwan's high-speed rail line

This paper develops a multiobjective programming model for the optimal allocation of passenger train services on an intercity high-speed rail line without branches. Minimizing the operators total operating cost and minimizing the passengers total travel time loss are the two planning objectives of the model. For a given many-to-many travel demand and a specified operating capacity, the model is solved by a fuzzy mathematical programming approach to determine the best-compromise train service plan, including the train stop-schedule plan, service frequency, and fleet size. An empirical study on the to-be-built high-speed rail system in Taiwan is conducted to demonstrate the effectiveness of the model. The case study shows that an optimal set of stop-schedules can always be generated for a given travel demand. To achieve the best planning outcome, the number and type of stop-schedules should be flexibly planned, and not constrained by specific stopping schemes as often set by the planner.

Evaluating airline competitiveness using multiattribute decision making

This paper presents an objective approach to the evaluation of airline competitiveness. The evaluation problem is formulated as a multiattribute decision making model and solved by three widely used methods (the simple additive weighting method, the weighted product method and the technique for order preference by similarity to ideal solution) based on multiattribute value theory. A new empirical validation procedure is developed to deal with the inconsistency problem of evaluation outcomes produced by the three methods. The procedure selects the evaluation outcome which has a minimum expected value loss. An empirical study on Taiwans five major domestic airlines is conducted to demonstrate the effectiveness of the approach. To measure and compare overall competitiveness of the airlines, five competitiveness dimensions and their associated objective performance measures on both efficiency and effectiveness are identified. The result of empirical validation for the three methods suggests the use of the simple additive weighting method. The evaluation outcome helps an airline identify its competitive advantages relative to its competitors. The objective approach presented is particularly applicable when subjective judgements on performance ratings and attribute weights are not reliable, or suitable decision makers are not available.

A new airline safety index

This paper develops a new quantitative airline safety index based on comparative safety performance and efforts of airlines. The index essentially indicates an airlines overall safety level, relative to other airlines in the context of safety competitiveness and risk. An empirical study of four major airlines in Taiwan is conducted to illustrate how the index is obtained. To facilitate the use of the index as a safety benchmarking and management tool, four safety dimensions corresponding to safety-related organizational divisions of airlines and their associated safety measures are identified. With the use of linguistic terms, subjective assessments of qualitative safety measures via surveys are represented with fuzzy numbers. The relative weights of safety attributes are assessed via surveys using a pairwise comparison process. Based on the concept of optimality, a fuzzy multiattribute decision making approach is developed to obtain a safety index for each airline. The airline safety index helps airlines understand their relative safety strengths and weaknesses in terms of manageable safety attributes, and identify functional areas for safety improvement.

Urban transportation energy and carbon dioxide emission reduction strategies

Abstract Sustainability is an urban development priority. Thus, energy and carbon dioxide emission reduction is becoming more significant in the sustainability of urban transportation systems. However, urban transportation systems are complex and involve social, economic, and environmental aspects. We present solutions for a sustainable urban transportation system by establishing a simplified system dynamics model with a timeframe of 30years (from 1995 to 2025) to simulate the effects of urban transportation management policies and to explore their potential in reducing vehicular fuel consumption and mitigating CO2 emissions. Kaohsiung City was selected as a case study because it is the second largest metropolis in Taiwan and is an important industrial center. Three policies are examined in the study including fuel tax, motorcycle parking management, and free bus service. Simulation results indicate that both the fuel tax and motorcycle parking management policies are suggested as potentially the most effective methods for restraining the growth of the number of private vehicles, the amount of fuel consumption, and CO2 emissions. We also conducted a synthetic policy consisting of all policies which outperforms the three individual policies. The conclusions of this study can assist urban transport planners in designing appropriate urban transport management strategies and can assist transport operation agencies in creating operational strategies to reduce their energy consumption and CO2 emissions. The proposed approach should be generalized in other cities to develop an appropriate model to understand the various effects of policies on energy and CO2 emissions.

A new method selection approach for fuzzy group multicriteria decision making

Fuzzy multicriteria decision making (MCDM) has been widely used in ranking a finite number of decision alternatives characterized by fuzzy assessments with respect to multiple criteria. In group decision settings, different fuzzy group MCDM methods often produce inconsistent ranking outcomes for the same problem. To address the ranking inconsistency problem in fuzzy group MCDM, this paper develops a new method selection approach for selecting a fuzzy group MCDM method that produces the most preferred group ranking outcome for a given problem. Based on two group averaging methods, three aggregation procedures and three defuzzification methods, 18 fuzzy group MCDM methods are developed as an illustration to solve the general fuzzy MCDM problem that requires cardinal ranking of the decision alternatives. The approach selects the group ranking outcome of a fuzzy MCDM method which has the highest consistency degree with its corresponding ranking outcomes of individual decision makers. An empirical study on the green bus fuel technology selection problem is used to illustrate how the approach works. The approach is applicable to large-scale group multicriteria decision problems where inconsistent ranking outcomes often exist between different fuzzy MCDM methods.

Airline e-commerce: the revolution in ticketing channels

This paper focuses on web reservation and on-line ticketing services provided by airlines and travel agents. The impact of the Internet on the air transportation industry in Taiwan, the development of e-commerce and e-business in airline operations, and the conflicts between virtual and physical channels are discussed. A questionnaire is developed to determine the major consumer behavior differences among channels. Some new trends and airline e-commerce issues are examined. The research outcome showed that virtual channels are good enough to dominate the market, but the traditional channels also have their own niches in some specific segments.

Human Performance Interfaces in Air Traffic Control

This paper examines how human performance factors in air traffic control (ATC) affect each other through their mutual interactions. The paper extends the conceptual SHEL model of ergonomics to describe the ATC system as human performance interfaces in which the air traffic controllers interact with other human performance factors including other controllers, software, hardware, environment, and organisation. New research hypotheses about the relationships between human performance interfaces of the system are developed and tested on data collected from air traffic controllers, using structural equation modelling. The research result suggests that organisation influences play a more significant role than individual differences or peer influences on how the controllers interact with the software, hardware, and environment of the ATC system. There are mutual influences between the controller-software, controller-hardware, controller-environment, and controller-organisation interfaces of the ATC system, with the exception of the controller-controller interface. Research findings of this study provide practical insights in managing human performance interfaces of the ATC system in the face of internal or external change, particularly in understanding its possible consequences in relation to the interactions between human performance factors.

Aviation occupant survival factors: An empirical study of the SQ006 accident

We present an empirical study of Singapore Airline (SIA) flight SQ006 to illustrate the critical factors that influence airplane occupant survivability. The Fuzzy Delphi Method was used to identify and rank the survival factors that may reduce injury and fatality in potentially survivable accidents. This is the first attempt by a group from both the public and private sectors in Taiwan to focus on cabin-safety issues related to survival factors. We designed a comprehensive survey based on our discussions with aviation safety experts. We next designed an array of important cabin-safety dimensions and then investigated and selected the critical survival factors for each dimension. Our findings reveal important cabin safety and survivability information that should provide a valuable reference for developing and evaluating aviation safety programs. We also believe that the results will be practical for designing cabin-safety education material for air travelers. Finally, the major contribution of this research is that it has identified 47 critical factors that influence accident survivability; therefore, it may encourage improvements that will promote more successful cabin-safety management.