Estimation of mental workload during automobile driving based on the measurement of eye and head movement

Abstract

The aim of this study was to investigate useful parameters of eye and head movement for estimation of mental workload (MWL) during automobile driving. Twelve students (6 males and 6 females) participated in this study. The participants performed a driving task with a driving simulator and a secondary task simultaneously. The N-back task was taken as the secondary task to control the MWL. The levels of N-back task were set as follows: None, 0-back, 1-back, 2-back, and 3-back. The gaze and head angles and blink frequency were measured with a visible-light image sensor. The eyeball rotation angle was calculated from the gaze and head angle. The sharing rate of head movement, which is the ratio of head movement against the gaze movement, was also calculated. In addition, the subjective MWL and accuracy of N-back task were measured. The result showed that the average subjective MWL monotonically increased with the increase of the difficulty of N-back task. The effect of the difficulty of N-back task was statistically significant for the standard deviations (SDs) of horizontal and vertical gaze angle, SD of horizontal eyeball rotation angle, sharing rate of head movement in horizontal direction, and blink frequency. The result of logistic regression analysis showed that the SD of horizontal eyeball rotation angle and blink frequency were the most significant parameters to estimate the MWL.