Evaluation of Driver's Mental Workload in Terms of the Fluctuation of Finger Pulse

Abstract

An investigation quantifying the fluctuation of finger pulse and detecting the situation that driver's mental workload is extremely high was carried out in a driving simulator. The Lyapnov exponent, which is one of the state variables quantifying the fluctuation of finger pulse, was evaluated in terms of the accuracy to detect the hazardous driving situation. The Lyapnov exponent will fluctuate according to the measuring condition or physical condition of driver. But, the normalized Lyapnov exponent, meaning the ratio of the Lyapnov exponent relative to that during the ordinary driving situation, fluctuate in the same range between 120 [%] and 180 [%], when the driver's mental workload is high. The threshold of the normalized Lyapnov exponent dividing the hazardous situation with ordinary driving situation is approximately 120 [%]. It is possible to estimate that the driver is facing the hazardous driving situation if the normalized Lyapnov exponent of the driver's finger pulse is higher than 120 [%].