Differential blink patterns as biomarkers: Quantifying visual cognitive load in curved tunnels with varied radii

This study aims to investigate the effects of curved tunnel geometries with varied radii on drivers' visual cognitive workload, utilizing differential blink patterns as biomarkers. The research seeks to quantify how tunnel curvature influences drivers' visual cognitive load and to identify potential biomarkers for assessing driving safety in curved tunnel environments.

Thirty licensed drivers with diverse driving experiences participated in the study. Eye movement data, including blink frequency, blink duration, inter-blink interval, and pupil diameter after blink, were collected using a Dikablis Pro eye tracker while participants drove through four curved tunnels with varying radii (185, 251, 493, and 1380 m) in Yunnan Province, China. A three-way repeated measures Analysis of Variance (ANOVA) was conducted to analyze the effects of tunnel radius, turning direction (left vs. right), and tunnel zone (entrance, middle, exit) on these blink metrics.

The study revealed significant main effects of tunnel radius, turning direction, and tunnel zone on all blink metrics. Specifically, as tunnel radius decreased, drivers exhibited lower blink frequency, shorter blink duration, longer inter-blink intervals, and larger pupil diameters after blinking, indicating increased visual cognitive load. Left turns were associated with higher cognitive load compared to right turns, as evidenced by lower blink frequency, shorter blink duration, longer inter-blink intervals, and larger pupil diameters. Blink patterns also varied dynamically across tunnel zones, with the entrance zone eliciting the highest cognitive load, followed by the middle and exit zones.

Differential blink patterns serve as reliable biomarkers for quantifying visual cognitive load in curved tunnels. Tunnel radius, turning direction, and tunnel zone significantly influence drivers' visual cognitive workload. These findings provide valuable insights for tunnel design and safety evaluations, emphasizing the need to consider geometric constraints and directional factors to reduce cognitive load and enhance driving safety.