# Situational Awareness Assessment of Drivers Boosted by Eye-Tracking Metrics: A Literature Review
## 3 Results
### Eye Trackers: Definition and Types  
In this review, we identified and examined a total of 24 distinct eye-tracking devices, each playing a role in the conducted experiments. These findings are documented in Table A2 of Appendix A; these findings are further shown in Figure 9. Tobbi Pro and X2-60 glasses were the most used eye trackers in all the studies considered in this review, and Pupil Lab using Python API was the second most used eye tracker. SmartEye Pro and DR120 were the third most used eye trackers, and Fovio and Eyelink with Eye Works Suite were used, albeit less frequently, within studios. An eye tracker is a device based on pupillometry, and a sensor captures the human eye movement by recording gaze points that indicate where a human is looking in an environment with a stimulus and measuring how many gaze points are registered per second [15; 16; 17]. The advantages of each eye tracker are interpreted by the communication between the device and data storage, analysis software, ease of interpreting the data, and data visualization, as well as the fact that the equipment is as less intrusive as possible for the operator; less intrusive equipment allows the process to continue without interruptions and ensure proper calibration time. With regard to demographics and cultural characteristics, reference [31] considered the difference in pupil color between Asians and Caucasians,  
Figure 9: Preferred eye trackers by number of experiments in which their use is reported. Orange bars indicate the primary eye tracker associated with each experiment. and [42] reported large cultural SA differences between drivers hailing from Japan and the USA. In addition, reference [59] found that teenage drivers have a lower level of SA than adults while driving. In the experiments, particularly in naturalistic driving experiments, daylight can be unpredictable because of dynamic conditions and can cause difficulties in reading the device data by the human eye; hence, reference [31] used illuminators to illuminate the driver's retina to compensate for the dim ambient light. Reference [33] used an infrared (IR) illuminator to reduce the effects of poorly illuminated environments; because IR is not visible to the human eye, it does not distract the driver. Additionally, note that several of the eye trackers generate some interference with the equipment used by the operator, and frequencies greater than 50 Hz are preferable for eye trackers. Finally, it is noteworthy that, for the assessment of potential biases arising from incomplete or unavailable data, a manual approach was employed for the total of reviewers. At the outset, a comprehensive search strategy was accomplished within the literature review to minimize the risk of overlooking relevant studies. The use of databases and conference proceedings contributed to this endeavor. In some instances, authors were contacted to gain access to their studies. For instance, [PERSON] [44] affably provided complete access to his publication. Additionally, the reviewers systematically categorized the criteria used to determine which results were eligible for inclusion. In this context, the criteria were grouped into the following: (1) Keywords and co-occurrence analysis in publications for scientometric analysis. (2) Demographic information, including sample size, gender, age, and any other relevant factors such as experience in the function. (3) The type of vehicle used in the experiment, categorized as either commercial or industrial. Metrics that were collected through eye tracking and reported included fixations, saccades, smooth pursuit, tremor, microsaccades, drift, blinks and their classifications, pupillary measures, gaze, and peripheral vision. Furthermore, the reviewers included a synthesis of the experimental environment in the results. These were grouped into naturalistic driving or driving simulations, selected from the reports, and documented the specifics of each experiment.