## 1 Introduction
In addition to being able to discern the drivers' states, eye movement visual features, fixation points, eye movement scan amplitude and average fixation time can also serve as indicators for evaluating drivers' physiologies and behavior, which could provide a basis for designing tunnel entrances and exits with safety considerations [14; 15; 16; 17]. In the context of indoor simulation experiments, pupil diameter and heart rate growth (HRG) were employed as indicators to investigate the influences of tunnel arch color on the drivers' behavior. These studies have revealed the significant impacts of tunnel arch color on both the drivers' pupil diameters and HRG, thereby concurrently affecting their operational performance and eye movement behaviors [18; 19; 20]. Research on eye movement parameters can provide further support for the safety design of tunnel entrances. Experiments were conducted using an eye-tracking system to obtain drivers' eye movement parameters when passing through highway tunnels. Analysis on the patterns of these parameters suggested that a rapid decrease in brightness can cause changes in fixation position and duration, so it was suggested to use measures that provide shade at tunnel entrances [21; 22; 23]. Eye movement parameters have also been utilized to investigate the illumination design within tunnels. In a study conducted by [PERSON] [24], the participants' reaction times, rates of change in the pupil area and blink frequencies were measured through indoor visual performance experiments and quantitatively represented the antagonistic mechanism between luminance intensity and luminance difference. The researchers established the Lav-U1 curve, which adhered to the safety threshold for the comprehensive visual efficiency of drivers. Furthermore, [PERSON] determined the length of the enhanced lighting section for the tunnel by examining the drivers' abilities to perceive target objects under dynamically changing lighting conditions [25]. Driving in tunnel segments not only affects eye-related visual parameters but also the psychological parameters of drivers. [PERSON] pointed out that tunnel entrances and exits create psychological loads on drivers and affect their safety by compiling and summarizing data from 1119 tunnels in 37 motorways over a 32-year period. Therefore, it is recommendedto optimize tunnel entrances and exits so as to ensure the safety of drivers in tunnels [26]. In addition to investigating tunnel entrances and exits, research scholars have also examined various human physiological responses in relation to tunnel slope, luminance of the tunnel light environment and the lowest point of river crossing tunnels. For instance, experimental findings on tunnel slope revealed its significant impact on heart rate variability and vehicle speed, thereby obtaining a safe gradient and travelling speed when driving uphill and downhill in urban underpass tunnels [27]. Regarding the study on the luminance of the tunnel light environment, researchers discovered a close relationship between drivers' perception of environmental brightness and their physiological as well as psychological states within long tunnels. To enhance illumination performance, driving safety and energy efficiency without increasing light source intensity, a method involving contour markers was proposed to regulate non-visual effects [28]. Furthermore, maximum heart rate variability and average heart rate variability can be used as physiological indicators to assess a driver's physiological load, and then to assess the safety of the lowest point in an urban river crossing tunnel [29]. The aforementioned contents revealed that visual feature data and psychological reactions constitute the primary focus of biomass research in tunnel studies. These investigations not only provide guidance for tunnel entrance construction but also inform the design of lighting environments in the tunnel structure and the enhancement of overall operational safety.