Let us try to explain why fuzzy logic systems were developed for transportation engineering. Great many of the problems in the field of transportation planning and traffic control are often ill defined, ambiguous and vague. As already mentioned, many traffic and transportation problems, phenomena and parameters are characterized by subjectivity. The concept of a fuzzy logic system (FLS) or concept called ‘Approximate Reasoning’ as follows: ‘In general a FLS is a nonlinear mapping of an input data (feature) vector into a scalar output (the vector output case decomposes into a collection of independent multi-input/ single-output systems). It showed that vague logical statements enable the formation of algorithms that can use vague data to derive vague inferences. Fuzzy set theory techniques need to be used in order to properly model traffic and transportation problems characterized by ambiguity, subjectivity and uncertainty.Some applications of Fuzzy Logic in transport planning are discussed below.