They consider the simplest case when the user is to choose one of two possible paths between the origin and destination of movement. Perceived travel time is very often ‘fuzzy’ and can be treated as a fuzzy set. In other words, when subjectively estimating travel time between two points. it is assumed that users choose their paths based on a comparison of the characteristics of alternative paths. Despite the fact that travel time is a measurable parameter, a driver's notion of travel time when he/she makes the route choice is often fuzzy. Thus, driver's preference for a route is based on a comparison of two fuzzy numbers. As a result, his/her certainty of choosing a route is also not crisp. The route choice model can represent the decision process under two layers of uncertainty: driver's judgment of time and driver's preference.