How periodic decorations in extra-long highway tunnels affect driving safety: A simulation study

OBJECTIVE: The enclosed environment and monotonous driving conditions of extra-long tunnels often induce driver fatigue and unstable operations, undermining both safety and comfort. As an effective intervention, tunnel landscape decoration zones are designed to alleviate fatigue, enhance alertness, and improve driving continuity. To investigate the influence of tunnel landscape decoration zones on driving behavior, this study evaluates their comprehensive effects across vehicle operation characteristics, physiological responses, and visual behavior, while proposing optimization strategies. METHOD: This study used the under-construction Qingdao Jiaozhou Bay Second Subsea Tunnel in China as a case study. Twelve simulated landscape schemes were constructed within a driving simulation environment, culminating in a total of 28 samples. Multidimensional driver data-including vehicle operation, eye movement, and heart rate-were collected and analyzed. RESULT: Results show that patterned vaults and periodic sidewall design significantly improve operational stability, while a proper pattern spacing provides the optimal balance between visual stimulation and cognitive load. Among all tested conditions, featuring sidewall-consistent vault patterns, periodic sidewall design, and 15 m spacing achieved the best performance in both safety and comfort. CONCLUSION: These findings provide theoretical foundations and practical guidance for the systematic design and environmental evaluation of extra-long tunnels.