## 5 Evaluation Results and Discussion  
### Collision Occurred HUD vs. HDD  
The comparative study between HDD and HUD aimed to identify the benefits and the potential drawbacks of both systems and with a particular interest in the efficiency of information access and provision of the proposed system. The collision results offer a clear and concise manner of revealing the aforementioned. The derived collision occurrence results of this comparison are presented in detail in Figure 12.  
Notably, the use of traditional touchscreens positioned within the dashboard estate (HDD) presented 87% collision occurrences. In contrast, when the HUD system was deployed, a sharp decrease of 64% in collisions was observed, whereby only 23% of participants experienced a collision in the simulated accident scenario. Beyond the duality of a positive and negative result of the collision occurrences, it was observed that each user had a different number of collisions throughout the simulation until the simulation events were completed. The number of collisions per trial is indicative of the amount of driver's distraction while attempting to circumvent the traffic and respond to the different incoming information as illustrated in Figure 13. Notably, the simulation was not terminated in the first collision, but the driver was allowed to continue the simulation until he/she reached the main collision event. Yet, throughout the simulation, the driver was tested and challenged by the AI-controlled vehicles which created mini-collision collision conditions which tested the driver's capability to respond and maintain the focus on the driving task. The drivers that were preoccupied with the interior infotainment systems tended to collide multiple times before the main collision event. Additionally, the timing of the accidents and the intensity of collisions could reveal the exact moment that each user experienced a cognitive overload and the time required to respond and attempt to amend the vehicle speed and lane positioning. Further observation of the driving patterns indicates that 6.5% of the users had no collisions with and without a HUD. However, on the post-trial debriefing, they highlighted that although they managed to avoid collisions, they felt more relaxed to operate the HUD system in contrast to the HDD, which required additional effort. Furthermore, the HDD arm of the simulation entailed in total 127 collisions amongst 26 participants, in comparison to the HUD which produced only 15 collisions between 7 users. As such, their driving pattern with the HUD did not present any erratic behaviour such as observed with the HDD in which they had to perform abrupt braking or lane change to avoid an imminent collision. Only 3% of the participants' sample (1 user), performed worst with the HUD interface, although experienced collisions in both simulations, with and without the HUD. The particular user found it difficult to operate the HUD interface and access the incoming data primarily due to the user's preferred seating position that prevented the operation within the active area of Leap Motion. A statistical analysis of the collision occurrences results presented previously in Figure 8 suggests that the HUD system offers a higher probability of collision avoidance with a confidence interval of 95%. The collision occurrences results were extrapolated from the 30 participants sample to the overall population of drivers with the use of large sample confidence interval (CI) for the population mean. The results were calculated with the confidence of 95%, which suggests a margin of 5% of potential error that is acceptable for the nature of this evaluation. The analysis highlighted that drivers have a probability of average 87% (1.00-0.74) to collide when they use the HDD for a mobile-phone messaging system and navigation updates on the  
Figure 12: Number of collisions recorded with HDD vs. HUD interface.