# Towards Understanding Driver Acceptance of C-ITS Services--A Multi-Use Case Field Study Approach
## 3 Results
### Test Drive Results  
The test drives in the ESRIUM project and the ASFINAG study analysed eye movement indicators. Fixation and gaze points are key metrics in eye-tracking research. A gaze point represents the basic unit of measurement--each one corresponds to a raw sample captured by the eye tracker. For instance, if an eye tracker records at 60 Hz (60 times per second), each gaze point represents 16.67 milliseconds. When multiple gaze points occur close together in time and space, they form a fixation--a period during which the eyes remain focused on a specific object. Fixation durations typically range from 100 to 300 milliseconds [28]. The field studies primarily examined attention to and distraction from C-ITS in-vehicle information. In both field studies, a so-called \"area of interest\" (AOI) was specified. The AOI includes the smartphone or tablet where the information is displayed to the driver (see Figure 11 from the ESRIUM project). This AOI signals the manoeuvre request. Table 8 lists dwell times, assumed distances driven while dwell time, and counts related to fixations and revisits as a result of the truck's drives. Fixations last on average 0.468 s, i.e., 10.4 m driven at a speed of 80 km/h. The minimum of fixations is 66 milliseconds, whereas the maximum is 1.56 s, and the average is 468 milliseconds. This translates to distances driven, while Dwell time ranges from 1.47 m to 23.47 m.  
While driving, altogether 6 manoeuvres (2 \(\times\) Lane Change Left, 2 \(\times\) Lane Change Right, 2 \(\times\) Lane Offset) were requested of the truck driver on the motorway. The fixation metrics for 9 truck drivers indicate that, on average, a truck driver performs a fixation five times, ranging from a minimum of 1 fixation to a maximum of 12 fixations. Revisits to the AOI range from 0 to 10 times (average 3). Figure 11: Definition of Areas of Interest. Additionally, heat maps for truck drivers' gaze points and fixations were generated within the analysis. The heat maps confirm that the main attention of the truck driver is given to the vehicles in front of the truck. Minor attention is given to the tachometer. The number of fixations and gazes in the area of the tablet does not indicate a cluster. In other words, minor attention was given to this area by the drivers on the motorway. However, the truck drivers noticed the information provided and complied with it in case the surrounding environment allowed them to do so. In the ASFINAG study, the reaction time to a change on the display was evaluated for eight car drivers, every use case focusing on the first and second sign of every use case (i.e., pre-warning \"in 500 m\" and first warning sign) to assess the information awareness. The average reaction time (duration between activating the sign on the display and first gaze on the display, considering all use cases and test drivers) is shown in Table 9.  
Looking at both car driver groups, i.e., professional and non-professional drivers, there is no significant difference in the reaction times. On average, the car drivers looked at the display for the first time 50 m after activating the sign, considering the speed limit of 100 km/h. There are high and low values in every group. Additionally, the is no dependency of the reaction time on the use case and signs displayed. The fixation-based parameters in Table 10 show that, on average, car drivers fixated (i.e., looking more than 100 ms on the display of the smartphone) the display 7.5 s and did that 71 times in the 700 s of the test lap. These values are a strong indication that the signs attract the attention of the car drivers. The gaze-based parameters in Table 10 show that, on average, test drivers looked at the display 109 times and in total 49 s on the display during the test lap lasting 700 s. The