Exploring drivers’ psychological responses in spiral tunnel: visual attention and subjective perceptions

The objective of this study was to investigate the challenges associated with driving in spiral tunnels through a comprehensive analysis of both visual performance and subjective perceptions of drivers. By comparing driving behavior in spiral tunnels to that in conventional curved tunnels, the study aimed to identify specific differences in visual attention, cognitive processing, and perceived workload, ultimately informing tunnel design and safety improvements. Naturalistic driving experiments were conducted in two different tunnel environments: A conventional curved tunnel and a spiral tunnel. Participating drivers were equipped with eye-tracking device to measure visual performance indicators such as average fixation duration, average pupil diameter, average saccade duration, and average saccade amplitude. Additionally, drivers’ subjective perceptions of workload were assessed using the National Aeronautics and Space Administration Task Load Index (NASA-TLX) scale, which evaluates mental, physical, temporal, and emotional demands, as well as overall performance and frustration. The results of the study revealed significant differences in drivers’ visual performance and subjective perceptions between spiral and curved tunnels. In spiral tunnels, drivers exhibited longer average fixation durations and larger average pupil diameters, indicating increased cognitive processing and visual attention requirements. Furthermore, drivers in spiral tunnels had longer average saccade durations and smaller average saccade amplitudes, suggesting a more cautious and focused visual scanning strategy due to the tight turns and limited visibility. Subjectively, drivers reported significantly higher workload across all dimensions of the NASA-TLX scale in spiral tunnels, indicating greater mental, physical, temporal, and emotional demands compared to curved tunnels. This study reveals the challenges of spiral tunnels for drivers, especially regarding visual attention and cognitive load. It suggests that improving tunnel design elements like lighting, signage, and road surfaces can lower drivers’ cognitive demands and improve their visual processing. The research also emphasizes the importance of specialized driver training for navigating these tunnels safely. In summary, the findings enhance transportation safety by offering insights into driving behavior in complex tunnels and suggesting methods to reduce risks.