Treatment of Uncertainty in Study of Transportation: Fuzzy Set Theory and Evidence Theory

Abstract

This paper examines the nature of uncertainty present in transport planning and explores appropriate mathematical treatment. Two types of uncertainty are dealt with: vagueness and ambiguity. The former refers to the uncertainty caused by the lack of definition of words, and the latter refers to the uncertainty caused by the lack of information about the subject matter. The mathematical framework that can deal with vagueness is fuzzy set theory, and that for ambiguity is evidence theory. Differences in the nature of problems that these two types of uncertainty present are examined. How to apply the appropriate mathematical technique to model these types of uncertainty is discussed, along with the basic properties of fuzzy set theory and evidence theory. Domains of transport problems that are conducive to these theories are explained, and the issues that need to be examined when using these theories are discussed.