The Pennsylvania State University The Graduate School Department of Civil and Environmental Engineering A GENERALIZED APPROACH FOR ANALYZING TRANSPORTATION USER PERCEPTION USING FUZZY SETS A Thesis in Civil Engineering by Dongmin Lee © 2006 Dongmin Lee Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2006 The thesis of Dongmin Lee was reviewed and approved* by the following: Martin T. Pietrucha Associate Professor of Civil Engineering Thesis Advisor Chair of Committee Sunil Sinha Assistant Professor of Civil Engineering Eric T. Donnell Assistant Professor of Civil Engineering Charles E. Antle Professor Emeritus of Statistics Andrew Scanlon Professor of Civil Engineering Head of the Department of Civil and Environmental Engineering *Signatures are on file in the Graduate School ii ABSTRACT A new approach for analyzing transportation user perception was developed using the concept of fuzzy sets. Due to the capability of fuzzy techniques to analyze subjective and uncertain matters, fuzzy set theory is an extremely useful tool for analyzing transportation user perception. To amplify the strength of the fuzzy approach for analyzing transportation user perception, several critical issues related to applying fuzzy techniques were reviewed, and existing fuzzy methods were adapted for use in the analysis of transportation problems. These new methods included procedures to determine fuzzy membership functions and to generate fuzzy rules This dissertation details the procedures followed to accomplish these tasks. First of all, appropriate types of fuzzy techniques, a fuzzy aggregation method and fuzzy inference system, identified from information about the various fuzzy set theories were selected based on a review of the related literature, studies related to transportation user perception, and previous fuzzy applications. Based on the selected fuzzy techniques, generalized fuzzy approaches for analyzing transportation user perception were developed. To develop these fuzzy approaches for transportation analysis, several details related to how each of the fuzzy approaches is applied were investigated. First, the relevant methods used to construct fuzzy membership functions for analyzing transportation user perception were identified. The use of these methods was illustrated by a series of real world applications as well. Second, the application of the fuzzy inference system, which is the most commonly used technique in fuzzy application studies, was explained. The appropriate ways to determine the structure of the fuzzy inference system and to generate the fuzzy rules were developed based on an understanding of the problems associated with analyzing transportation user perception. Third, a comparison was conducted between the perception of users from the general public and transportation experts. To investigate the applicability of using the opinions of groups of experts regarding the service quality of transportation systems as the surrogate of the opinion of groups of transportation users, statistical comparisons between the two were conducted. iii To improve the developed fuzzy approaches and increase their applicability, two different transportation case studies using each of the two developed fuzzy approaches were conducted. The service quality of variable message signs (VMS) based on driver perception was evaluated using the fuzzy aggregation method. Existing survey results regarding the service quality of VMS were re-analyzed, and the overall satisfaction of the service of the VMS were aggregated. Experts’ opinions of crash factors associated with design and operational aspects of medians were incorporated using a hierarchical fuzzy inference system to evaluate median safety. Through the developed system, the degrees of median safety for real roadway segments were evaluated. Then, they were compared with observed median crash data. Finally, two preliminary methods of validating fuzzy results were used, direct validation and indirect validation. An experimental study evaluating the service quality of signalized intersections was conducted to apply the direct validation. Using the observed crossover median crashes (CMC), the indirect validation method was applied. Based on these two preliminary validations, the developed fuzzy approach was found to be a suitable method for analyzing what drivers generally perceive from transportation systems when the unique characteristics of humans as transportation users is considered. In conclusion, since transportation user perception is affected by many factors and the magnitude of the effect of each factor on transportation user perception is different between factors and between users, analyses considering those differences can produce better results in solving many types of transportation problems. For analysis of transportation user perception, the developed fuzzy approach can appropriately analyze user perception and produce more accurate and conceptually realistic results. The basic concepts and specific procedures of the fuzzy approach developed herein can help to analyze appropriately transportation user perception. More accurate and realistic analysis of transportation user perception is enormously important for providing better transportation service to the public. The developed fuzzy approach enables designers and system operators to understand transportation user perception more thoughtfully, which can lead to a transportation system that is more conducive to providing service that leads to greater user satisfaction. iv TABLE OF CONTENTS LIST OF FIGURES .....................................................................................................viii LIST OF TABLES.......................................................................................................xi ACKNOWLEDGEMENTS.........................................................................................xiv CHAPTER 1 INTRODUCTION ................................................................................1 1.1 Research Objectives........................................................................................3 1.2 Scope of Research...........................................................................................4 1.3 Organization of Thesis....................................................................................5 CHAPTER 2 LITERATURE REVIEW .....................................................................7 2.1 Studies Related to Evaluation of Transportation User Perception .................7 2.2 Fuzzy Set Theory............................................................................................11 2.2.1 Introduction of Fuzzy Set Theory.........................................................11 2.2.2 Classic Set and Fuzzy Set.....................................................................11 2.2.3 Probability Theory and Fuzzy Set Theory............................................12 2.2.4 Membership Function...........................................................................13 2.2.4.1 Types of Fuzzy Membership Function.......................................14 2.2.4.2 How to Interpret the Grade of Membership Function................17 2.2.4.3 Fuzzy Inference System .............................................................18 2.3 Fuzzy Application Related to the Proposed Study .........................................21 2.3.1 Transportation Engineering..................................................................22 2.3.2 Decision Making Processes..................................................................27 2.3.3 Evaluation of Service Quality in Non-Transportation Engineering Fields ......................................................................................................29 2.4 Summary.........................................................................................................31 CHAPTER 3 METHODOLOGY ...............................................................................33 3.1 Development of a General Methodology (Task 1).........................................35 3.1.1 Feasible and Appropriate Types of Approaches for Analyzing Transportation User Perception using Fuzzy Set Theory.......................36 3.1.2 How to Construct Membership Functions............................................36 3.1.3 How to Design the Experiment for the Fuzzy Approach .....................37 3.1.4 Developing the Fuzzy Inference System..............................................37 3.1.5 Comparison of Expert Perception with Public Perception...................38 3.2 Application Studies (Task 2) ..........................................................................38 3.2.1 Evaluation of VMS Service Quality.....................................................39 3.2.2 Evaluation of Median Safety................................................................40 v 3.3 Validation of the Analysis Results of Transportation User Perception based on Fuzzy Approaches ..........................................................................41 CHAPTER 4 DEVELOPMENT OF A GENERALIZED FUZZY APPROACH FOR ANALYZING TRANSPORTATION USER PERCEPTION.....................42 4.1 Introduction.....................................................................................................42 4.2 Two Approaches for Analyzing Transportation User Perception Using Fuzzy Set Theory...........................................................................................42 4.2.1 Evaluation of Transportation