## 5 Evaluation Results and Discussion
### Indicative Driving Patterns-Discussion  
Four indicative driving patterns are presented based on the collision occurrences with the HUD and HDD devices. In particular, these include (A) collision with HUD and with HDD, (B) no collisions with HUD and no collisions with HDD, (C) large number of collisions with the use of HDD, and (D) no collisions with HUD and collisions with HDD, which was the result of the largest group in the experiment as presented in Figure 15. \begin{table}
\begin{tabular}{c c c} \hline \hline
**HDD** & **CI \(n\) = (30) x = (26) c = (0.95)** \\ \hline \multirow{4}{*}{Collisions with HDD} & Mean & 0.87 \\ \cline{2-3}  & 95\% CI for Mean & Lower Bound & 0.74 \\ \cline{2-3}  & Upper Bound & 1.00 \\ \cline{2-3}  & 5\% Trimmed Mean & 0.83 \\ \cline{2-3}  & Variance & 0.120 \\ \cline{2-3}  & Standard Deviation & 0.346 \\ \hline HUD & CI n = (30) x = (7) c = (0.95) & \\ \hline \multirow{4}{*}{Collisions with HUD} & Mean & 0.23 \\ \cline{2-3}  & 95\% CI for Mean & Lower Bound & 0.07 \\ \cline{2-3}  & Upper Bound & 0.39 \\ \cline{2-3}  & 5\% Trimmed Mean & 0.20 \\ \cline{2-3}  & Variance & 0.185 \\ \cline{2-3}  & Standard Deviation & 0.430 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Probability of collision occurrences for HDD and HUD with CI 95%. Figure 14: User experience results regarding the ease of use for the HUD interface. The first set of graphs (Figure 15A) highlights some driver responses which have been similar to both HDD and HUD devices and resulted in both cases in collisions. The five users of this category produced an equal amount of HUD and HDD collisions (2 users) and in some cases a higher number of collisions with the use of HUD (3 users). This can be attributed to a number of potential issues or combination of issues related to the simulation environment (i.e., seating position), the driver (i.e., height), and lack of familiarisation with the new system amongst other. Further, it could reflect the cognitive load that for some users is similar for both systems. Additionally, the interface design or interaction could not  
Figure 15: Four indicative driving patterns defined by the collisions occurred with the use of HUD and HDD: (**A**) collision with HUD and with HDD, (**B**) no collisions with HUD and no collisions with HDD, (**C**) large number of collisions with the use of HDD, and (**D**) no collisions with HUD and collisions with HDD. be intuitive for some users. Although it is expected that a system could not facilitate all the users, it would be interesting to investigate further the reasons and identify potential solutions that could enable more users to operate the proposed system. The following graph (Figure 15B) presents another group of four users who managed to avoid all the potential collisions whilst operating the HDD or the HUD. Their driving patterns followed closely the response of the lead vehicles and manoeuvred appropriately or decelerated without getting involved in any of the accident scenarios developed by the AI-controlled vehicles. In contrast, five users were involved in more than 10 accidents each while they were using the HDD infotainment system. One of the users had also one collision with the HUD. The high number of collisions highlights the detrimental effects for some users when they split their attention and take their eyes off the road. Interestingly the rest of them had no collisions with the HUD. Investigating further the driving patterns that appeared on the simulation, an indicative common user reaction (16 users) is presented in the graphs of Figure 15D. Focusing into the last few seconds of the final collision of the driver D the following two graphs (Figure 16a,b) present the users' (a) speed vs. time and (b) distance from the lead vehicle vs. time. In particular, the Figure 16a graph shows the user's vehicle speed (Km/h) and the time travelled (s) prior to the imminent collision scenario with the lead vehicle. Figure 16: Driver reactions on the last 13 s of the simulation.