Recently, the analysis and application of biosignal is attracting great attention. In particular, the estimation of human internal state based on the electroencephalogram (EEG) signal is a promising strategy because of its huge amount of information. In this paper, first of all, the EEG signal under the driving situation is captured synchronizing with the behavioral signals such as the pedal operation. Then, the 'mode' underlying the observed EEG signal is extracted by applying the stochastic switched autoregressive (SS-AR) model. Finally, the meaning of each mode is investigated from viewpoint of the correspondence with the driver's internal state.
