When solving real-life engineering problems, linguistic information is
often encountered that is frequently hard to quantify using "classical"
mathematical techniques. This linguistic information represents
subjective knowledge. Through the assumptions made by the analyst when
forming the mathematical model, the linguistic information is often
ignored. On the other hand, a wide range of traffic and transportation
engineering parameters are characterized by uncertainty, subjectivity,
imprecision, and ambiguity. Human operators, dispatchers, drivers, and
passengers use this subjective knowledge or linguistic information on a
daily basis when making decisions. Decisions about route choice, mode of
transportation, most suitable departure time, or dispatching trucks are
made by drivers, passengers, or dispatchers. In each case the decision
maker is a human. The environment in which a human expert (human
controller) makes decisions is most often complex, making it difficult
to formulate a suitable mathematical model. Thus, the development of
fuzzy logic systems seems justified in such situations. In certain
situations we accept linguistic information much more easily than
numerical information. In the same vein, we are perfectly capable of
accepting approximate numerical values and making decisions based on
them. In a great number of cases we use approximate numerical values
exclusively. It should be emphasized that the subjective estimates of
different traffic parameters differs from dispatcher to dispatcher,
driver to driver, and passenger to passenger.