We conducted below:
(1) We used bio signals and driving information signals that are measured by the driver’s body and the vehicle’s body for estimating the driving road from the signals. Furthermore, we estimated driving load assuming use of sensors obtained by smartphones. (2) We evaluated the spoken dialog strategy from the viewpoint of user’s driving load. An objective evaluation by computer simulation was conducted by considering both dialog initiatives and the exitance of confirmation utterances. (3) We conducted a subjective evaluation to evaluate the performance of the proposed dialog strategy as a spoken dialog system. The subjects were asked to drive a simulator during talking with a spoken dialog system. (4) A dialog strategy based on graph search was introduced to realize a dialog strategy which considering the estimation result of the user's mental load. We evaluated the proposed system by objective evaluation and subjective evaluation.