Assessing tunnel entrance guidance in agglomerate fog via driver perception-behavior coordination

OBJECTIVE: Agglomerate fog at tunnel entrances creates a coupled hazard of sudden visibility loss and luminance transition, yet its effect on driver perception-behavior coordination is underexamined. This study investigates how visibility and multi-level guidance facilities influence such coordination. METHODS: Driving simulation experiments with 21 drivers were conducted under two visibilities (50 m and 200 m) and four guidance configurations (basic, information-enhanced, speed-control, integrated). Dynamic time warping (DTW) clustering, behavior sequence analysis, and a coupling coordination degree model were applied. RESULTS: (1) At 50 m visibility, drivers adopted a conservative strategy: speed reduced by approximately 60 km/h, fixation duration increased, and saccade scope narrowed. (2) Facility effectiveness was visibility-dependent; the integrated scheme (red fog lamps, dense layout, VMS, markings) performed best under agglomerate fog, as speed reduction markings alone attracted excessive gaze and suppressed saccades. (3) Enhanced facilities improved perception-behavior synergy; coupling coordination degree increased from basic to integrated scheme. At 200 m, advanced schemes approached saturation (diminishing returns). (4) Under basic facilities, coordination at 50 m (0.343) slightly exceeded that at 200 m (0.297), suggesting a tendency toward passive but tightly synchronized coordination under extreme conditions. CONCLUSIONS: The integrated guidance scheme robustly supports driver coordination in dense fog. The coupling coordination degree effectively quantifies system synergy. These findings guide optimal design of tunnel entrance guidance facilities under agglomerate fog.