The concept of intuitionistic fuzzy sets was firstly introduced by
Atanassov (1986), which is a generalization of fuzzy sets by adding
an additional non-membership degree. By using the intuitionistic
fuzzy sets, the incomplete information can be suitably described
by two characteristic functions (membership and nonmembership).
Typically, an intuitionistic fuzzy number (IFN) is a special
case of the intuitionistic fuzzy set, and the most common IFNs
are triangular intuitionistic fuzzy numbers and intuitionistic trapezoidal
fuzzy numbers.
In order to describe the quantitative analysis in high-speed railway
accidents under uncertain environment, this paper treats the
failure possibility of a basic event as an intuitionistic trapezoidal
fuzzy number to account for imprecision and uncertainty in data.
The following contents are about some basic concepts related to
intuitionistic trapezoidal fuzzy numbers