Assessment of drivers' visual search patterns and cognitive load during driving in curved tunnels

Objective: The objective of this study was to assess drivers' visual search patterns and cognitive load during driving in curved tunnels. Specifically, we aimed to investigate how different curved tunnel geometries (tunnel radii, turning directions) and zones (entrance, middle, exit) influence drivers' saccadic eye movements. This understanding can inform the development of safer tunnel designs and driving guidelines.

Methods: A total of 30 licensed Chinese drivers participated in the study. Eye movement data were collected using the eye tracker while participants drove through four experimental curved tunnels. Each tunnel differed in radius, turning direction, and zone. Eye movement parameters, including saccade duration, frequency, amplitude, and velocity, were analyzed to evaluate drivers' visual search patterns and cognitive load.

Results: The results revealed significant differences in drivers' saccadic eye movements across different tunnel conditions. As the tunnel radius decreased, drivers exhibited shorter saccade durations, increased saccade frequencies, decreased saccade amplitudes, and reduced saccade velocities, indicating increased cognitive load and more frequent visual updates. The turning direction also influenced saccadic behavior, with drivers demonstrating shorter saccade durations and higher frequencies when turning left compared to turning right. Furthermore, significant variations were observed across tunnel zones, with drivers showing the shortest saccade durations and highest frequencies in the entrance zone, while the mean saccade amplitude and velocity were largest in the exit zone.

Conclusions: This study provides valuable insights into how drivers adapt their visual search strategies and cognitive processes in response to varying curved tunnel conditions. The findings highlight the importance of considering tunnel geometry, turning direction, and tunnel zones in designing safer tunnel infrastructures and driving guidelines. Specifically, the results suggest that drivers experience increased cognitive load in narrower tunnels and during left turns, necessitating a more dynamic and frequent visual search strategy.