## 4 Evaluation Method and Simulation Requirements
### VR Driving Simulator  
To evaluate the proposed system, we developed a custom VR driving simulator. The latter could offer a controlled environment to experiment safely and ensure the repeatability of the simulation conditions [23,24]. The simulator accommodates a full-scale Mercedes A-Class 2003 car model, which was encapsulated in a Cave Automatic Virtual Environment (CAVE) room, as illustrated in Figure 7. The CAVE produces a fully immersive experience with 3D high-definition projections on all the surrounding walls. The simulator's interior was rebuilt to facilitate the testing of vehicular interfaces. In addition, the simulator interior is equipped and customisable with different types and positions of touchscreens for the simulation of various HDD infotainment systems. The dashboard instrumentation presents fully functional, digital versions, of a tachometer and speedometer. For the particular experiment, a Leap Motion sensor positioned on the top of the dashboard instrumentation hub for the facilitation of the gesture recognition. A 5.1 surround audio system ensures that the driver experiences the environmental noises as well as the engine, gearbox, tyres, and any other related sound during the simulation. Furthermore, the vehicular floor houses a set of vibrating devices providing realistic engine, road and collision vibrations. The simulation software records for each user trial, the collisions occurred, the driver's speed, the simulation elapsed time, the lane position, the distance from the lead vehicle, and the neighbouring vehicles every 0.03 s. The derived results are automatically calculated and present the driver's response times (RT) and headway (HW) during an imminent collision. As the simulation was not ending at the first collision, the number of collisions per user-trial was also logged. Additionally, the recording of the manoeuvring choices of each driver sketches a clear view of the driving patterns that emerge and the usability of the system under evaluation. Figure 7: Explanatory image of the VR driving simulator laboratory (VRDS Lab) set up. The vehicle interior accommodated the HDD in the form of a lower touchscreen (smart tablet) positioned in the existing screen-space that the manufacturer has provided for such systems which are located in the middle section of the dashboard in relatively close proximity to the user's extended arm and approximately 720-880 mm from the driver's eyes [14; 23]. Evaluation of multiple potential positions has been performed in-depth and results indicate that the following order, F, C, A, D, B, G, and E are the best to worst options as illustrated in Figure 8[46]. The selected HDD position, the upper part of the cluster/dashboard (C), used in this experiment, is the second-best position following the HUD projected in front to the driver's field of view (FOV) [46]. Notably, any other HDD position results in worse results for the HDD users as presented in previous studies [46; 47; 48]. In particular, this work compares the best possible HDD position (C) against the proposed HUD (F) which occupies a typical HUD space in the windscreen and appears to be embedded in the environment. For the proposed HUD, the AR symbols appear at 2.5 m ahead (bonnet level), extending further than the vehicle's bonnet, an improvement from the previous design to enhance the merging of the information to the external environment and reduce the strain of driver's focusing between AR information and exterior scene. This position is also identified by other relevant studies as the best position (F) for the projection of a HUD interface [46; 47]. However, the vast majority of infotainment systems are bound to the HDD space and typically positioned in the spaces D and E of vehicle dashboards. The positioning, size, and accessibility of the infotainment screens are also dependent on the vehicular interior-design style of each manufacturer, which can further differentiate between models.