## 2 Literature Review
Also, they analyzed the influence of delineator configuration on the tunnel driver's scanning path in tunnels [32], and quantified the complexity of individual switching patterns by Markov-based entropy method. The resultsshowed that subjects' interest areas varied with driving scenarios. Additionally, more than 50% of gaze time was spent on the left and tight curve portions of the straight-line section. [PERSON] [33] evaluated the impact of color decoration of interior tunnel walls on the driving characteristics. The subjective evaluation, constant speed driving duration, and lane offset of sixty licensed drivers were analyzed in the study. The investigation results demonstrated that under the same environmental information, there was no significant influence on subjective evaluation value of the subjects, and environmental data in the color decoration scheme had a significant effect on their constant speed driving duration. Although it is true that experiments conducted in driving simulators do have the advantage of being easier to accomplish, are less risky, and require less of a budget than those conducted on real roads [34], they have limitations which cannot reproduce the environment on the real road [35]. The second category is field research, carried out in real tunnel scenarios. [PERSON] and [PERSON] [36] used the corneal reflection eye-maker recorder to investigate eye movements of drivers while approaching tunnel entrances. In the study, two experienced male observers drove a car at speeds between 55 km/h and 100 km/h and stated the moment they began to focus their visual attention on the tunnel entrance in front. Analysis results demonstrated that the minimum duration of the eye mark fixed on a certain point was 0.1-0.2 s, and in some cases, eye marks tended to stay in a certain position on the road scene for a relatively long time. [PERSON] and [PERSON] [37] studied drivers' characteristics variation as they passed through the tunnel exit. They also used the BP neural network to establish a mathematical model of fixation time and eye saccade amplitude at the tunnel exit portal. Results indicated that the variation of drivers' visual characteristics changed based on the distance from the tunnel exit. Additionally, when approaching the tunnel exit, the fixation duration and number of fixation of drivers are reduced, while drivers' saccade amplitude at the tunnel exit is increased. [PERSON] et al. [19] collected test data of nine drivers at the tunnel entrance and inside sections to assess how drivers' visual features had changed during driving. The drivers' eye movement data showed an increase in the average values of fixation duration of 100 m outside the tunnel entrance, but a decrease in fixation number. In addition, drivers had a long-time fixation while driving through the tunnel. [PERSON] et al. [38] collected drivers' eye movement and pupil diameter together with their heart rate (HR) at the Xi'an men tunnel's entrance and exit. Factor analysis was used to extract a comprehensive measure that could reflect nanoscopic driving behavior. Analysis results concluded that, for the entrance zone, the road section (\(-40\) m, 40 m) is unsafe, which may cause the driving deceleration and increase in heart rate. Besides, the fluctuation rate of pupillary diameter is sharply in the section (\(-5\) m, \(25\) m). Moreover, attention should be paid to the 150 m to 110 m section before the vehicle exits the tunnel. [PERSON] et al. [39] used a head-mounted eye-tracking system to record the parameters of eye movement of thirty-two participants while driving under different spatial-visual conditions in the tunnel's entrance zone. Results indicated that route familiarization had a significant effect on the number of fixations, average saccade amplitude, and average speed. However, route familiarization had a weak influence on the fixation duration and average saccade speed.