Discrete wavelets have been applied to analyzing a R-R Interval tachogram. Consequently, a specific wavelet level indicates the dominant frequency that indicates driver's mental stress with the time process. This method is able to replace former Fourier base analysis in the driver's circumstances. The experiments are carried out with a driver carrying an electrocardiograph in a passenger car circulating a test course with 140km/h. The R-R Interval tachogram was obtained from the driver before and while driving. The motivation behind this work is to establish a driver's mental model while the driver operates a vehicle. The model contributes to safe and comfortable driver's circumstances.
