## 4 Results  
### Variables Extraction and Data Preprocessing  
From the records obtained in the.csv file of each simulation, numerical variables related to the use of the eye-tracking (hereinafter, ET) application and the kinematics of the cyclist and the vehicle are computed. Coordinates with a cyclist subscript indicate the position of the VRU at a given time, otherwise they denote the position of the vehicle as captured by the eye-tracker:  
* Time from when the cyclist first looks at the vehicle until the time of the accident or, failing that, until passing through the theoretical collision point (t1): \[\text{t}_{1}=\big{(}\text{timestamp}_{ET\_vehicle\_start}\big{)}_{1}-\text{ timestamp}_{ACCDENT}\] (1) where subscript 1 represents the first period of observation of the vehicle. If the accident does not occur, the timestamp corresponding to that event is replaced by the instant of time at which the cyclist passes through the theoretical point of collision, calculated as the intersection of the trajectories of the user and the vehicle. * Total time of the cyclist looking at the vehicle (t2) up to the time of the accident, calculated as: \[\text{t}_{2}=\sum_{i=1}^{n}\big{(}\text{timestamp}_{ET\_vehicle\_end}- \text{timestamp}_{ET\_vehicle\_start}\big{)}_{1}\] (2) where n is the number of observations up to the timestamp at which the accident occurs. If the accident occurs at a timestamp before the last END marker of the vehicle observation, the time t2 is worked out as the subtraction of the accident timestamp and the corresponding START marker. If it does not occur, the summation is calculated up to the timestamp at which the cyclist passes the theoretical point of collision. * Total distance traveled since the time the cyclist starts looking to the accident site (d1). Once the first instant of observation of the vehicle is identified, the timestamp correspondence with the headset record is sought to identify the position of the cyclist at that instant. The distance is calculated as: \[\text{d}_{1}=\sqrt{\frac{\big{(}\text{X}_{cyclist\_ACCDENT}-\text{X}_{cyclist\_ ET\_vehicle\_start}\big{)}^{2}-}{\big{(}\text{Z}_{cyclist\_ACCDENT}-\text{Z}_{cyclist\_ ET\_vehicle\_start}\big{)}^{2}}}\] (3) Note how the formula is applied regardless of whether the cyclist is traveling in the X- or Z-axis direction. If the accident does not take place, the final position of the cyclist is the one corresponding to the theoretical collision point. This assumption is valid for the rest of the distance estimations in which the use of eye-tracking is considered. * Total distance traveled looking at the vehicle before the accident (d2), calculated as: \[\text{d}_{2}=\sum_{i=1}^{n}d_{ET\_vehicle}\] (4)where \(d_{ET\_vehicle}\) is the distance traveled by the cyclist in each observation period (_i_) prior to the accident or theoretical point of collision. Each observation period \(i\) starts with an \(ET\_vehicle\_start\) and ends with an \(ET\_vehicle\_end\). * Relative distance between the cyclist and the vehicle at the instant the cyclist first sees the vehicle (d\({}_{3}\)), calculated as: \[\text{d}_{3}=\sqrt{ \begin{pmatrix}\left(X_{cyclist\_ET\_vehicle\_start}-X_{EET\_ vehicle\_start}\right)^{2}-\\ \left(Z_{cyclist\_ET\_vehicle\_start}-Z_{ET\_vehicle\_start}\right)^{2} \end{pmatrix} }\] (5) In this case, the X and Z position values of the vehicle are those indicated by the corresponding tracker in the first detection performed through eye-tracking. * Speed of the cyclist at the first instant when they spot the vehicle or first START_Vehicle (v\({}_{11}\)). * Speed of the cyclist at the moment of the accident or, failing that, when passing through the theoretical point of collision (v\({}_{1f}\)). * Vehicle speed at the instant of the accident or, failing that, when passing through the theoretical point of collision (v\({}_{2f}\)). * Cyclist operating time (t\({}_{01}\)), calculated as the time elapsed from when the cyclist initiates the reaction until the accident occurs or passes through the theoretical point of collision.