# Towards Understanding Driver Acceptance of C-ITS Services--A Multi-Use Case Field Study Approach
## 2 Methodology
### Driver Acceptance
#### 2.1.2 Test Drives  
The test preparation started with selecting test drivers who agreed to be monitored and interviewed. The group of test drivers included four female and fourteen male drivers, where ten people (male) were driving a truck and eight people (four male professionals and four female non-professional drivers) were driving a car (see Figure 3). The test drives with the trucks took place in July 2023, and the ones with the cars in November 2024.  
The test area was located on the A1 motorway next to Linz, Austria, for the test drives with the trucks, and on the S1 in the South of Vienna, Austria, with the cars. The motorway A1 has three lanes and a hard shoulder in each direction, while the motorway S1 has two lanes and a hard shoulder in each direction. The maximum speed limit is 130 km/h and 100 km/h, respectively.  
The test vehicles were standard trucks and cars. They were equipped, in addition to the built-in equipment, with a tablet or smartphone mounted next to the driver. The displayed information to realize the desired C-ITS service was manually triggered by the co-pilot, who knew the position of the events. The trigger points were specified before and remained the same for every test drive. The information was presented to the driver through pictograms displayed on a tablet or smartphone, and additionally, an acoustic alarm was provided.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Question Category** & **Reference to TAM** \\ \hline Demographic data & External variables (EV) \\ Profile & External variables (EV) \\ Accidents & External variables (EV) \\ Previous Knowledge & External variables (EV) \\ Compliance & Behavioural intention to Use (BI) \\ Desired Driving Information & External variables (EV), \\  & Behavioural intention to Use (BI) \\ C-ITS Services & Perceived Usefulness (U), Behavioural intention to Use (BI) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Overview of question categories and components of TAM.  
Figure 2: Technology acceptance model.  
To analyse the driving behaviour, eye tracking was chosen as an additional source of information. Within the tests, the mobile eye tracking glasses Pupil Invisible from Pupil Labs [26] were used to record the eye movements, video of the point of view of the test drivers, and the audio during the test drive.  
The test drives included six test scenarios.  
C-ITS service LCR (with trucks)  
1. Lane-Offset-Recommendation: Change to the left or the right within the same lane
2. Lane-Change-Recommendation: Change the lane  
C-ITS service RWW (with cars)  
3. Road Works Warning, right-most lane is closed: Reduce speed and change to the left lane  
C-ITS service HLN (with cars)  
4. Hazardous Location Notification, Emergency vehicle closes left-most lane: Reduce speed and change to the right lane
5. Hazardous Location Notification, Traffic jam ahead: Reduce speed, leave the motorway at the next exit  
C-ITS service IVS (with cars)  
6. In-vehicle signage, speed limit: Change speed to the displayed speed limit  
All the test drivers were interviewed before and after the test drives (see Table 4). The interview guidelines were primarily derived from the expertise of the C-Roads evaluation working group [22]. Each question category refers to a component of the TAM.