Impact of tunnel entrance/exit sidewalls and Medians on driver behavior: Operational safety risk diagnosis based on avoidance dynamics and trajectory evolution.

Tunnel entrance/exit represent critical transition zones within underground transport infrastructure with elevated accident risks. This study investigates driver avoidance behavior toward sidewalls and median strips under the alternating light-dark conditions and spatial constraints of these areas, aiming to mitigate human-space interaction risks during underground-to-surface transitions. Using UAV to collect vehicle driving data for Rail-cum-Road Yangtze River Cross Tunnel in Wuhan, China. Employing an "avoidance degree grading-risk pattern clustering" methodology, vehicle trajectory dynamics were quantified. Revealed drivers' spatial perception and avoidance behavior mechanisms, establishing a safety performance diagnosis and evaluation model. The main conclusions are as follows: 1) Drivers' avoidance behavior outside the tunnel is dominated by psychological expectations and post-adaptation effects. At the entrance, effective avoidance occurs in a "pre-initiated avoidance behavior" pattern. However, at the exit, difficulties in spatial re-evaluation arise due to "adaptive aftereffect" and the absence of external guidance facilities, leading to a high incidence of high-risk "complex conflict avoidance" (65.71% and 52.22%), highlighting the safety challenges posed by environmental transitions. 2) A seven-category risk spectrum of avoidance behaviors was established. Sidewalls were identified as the primary constraint for trajectory deviation. In the exit where sidewall constraints are released, the influence of the median strip is amplified (left deviation at entrance, right deviation at exit). The synergistic design of sidewalls with median is crucial for trajectory envelope and clearance safety. 3) Enhancing continuous visual guidance to align with drivers' psychological expectations and adaptation processes is crucial for improving operational safety in tunnel transition zones. This approach represents a fundamental shift in design philosophy, from passive spatial confinement to active behavioral guidance.