Drivers' visual characteristics in small-radius optically long tunnels on rural roads

This study aims to investigate drivers' visual characteristics under different radii and turning conditions in small-radius optically long tunnels on rural roads. Fixation and saccade were our main research objectives. We conducted real vehicle tests in optically long tunnels under four different radii. Using the distribution of gaze points, fixation duration, and fixation frequency, the drivers' fixation characteristics were examined. In addition, the drivers' saccade characteristics were examined by selecting the saccade duration, saccade frequency, and saccade amplitude. Accordingly, we established mathematical models of fixation duration and saccade duration with a radius under different turning conditions in different zones. Along with the visual task, we further examined drivers' characteristics in optically long tunnels. We found that the smaller the tunnel radius, the more focused gaze points on inside of the curves, the larger the fixation duration, and the lower the safety with higher psychological pressure. In the zone where the exit portal was invisible, drivers' tension and risk were higher during turning right, whereas drivers' tension and risk were higher during turning left in the zone that the exit portal was visible.