## 1 Introduction  
Contemporary infotainment devices are introduced in car interiors to provide crucial information related to the vehicle and different forms of audio-visual entertainment. Yet the number of devices, their position, and the attention-seeking interfaces have multiplied exponentially, following the infotainment trends provided by popular, non-vehicular conduits, such as smartphones and tablets. Notably, such devices were primarily designed to attract the user's attention, hence not compatible with the driving process. The vehicular devices replicate the incoming information and engross the driver's situational and spatial awareness through ineffective gazing at the dashboard's interactive screens. The latter provides a regularly updated stream of information facilitating satellite navigation and incoming mobile communications amongst other systems. As all the aforementioned information conduits are positioned within the vehicular dashboard, which is below the driver's field of view (FOV), they are forcing the driver to look down, hence these devices are also known as head-down displays (HDD).  
Due to their position, they can divert the driver's concentration from the primary task and result in misjuddgnment of traffic conditions and vehicle control requirements [1; 2]. As such, in a collision-prone situation, the driver's reaction/response time (RT) is reduced significantly [3; 4; 5]. Amongst the plethora of devices and applications located in the dashboard, some have been particularly distracting as they require the driver's immediate attention and response, such as mobile phone communication (mobile call and texting), [6; 7; 8; 9], and navigation guidance systems [10; 11]. Notably, the imposed cognitive load to the driver in both cases can rapidly reduce the concentration in the main task and result in collisions, as the driver suffers from an attention bottleneck due to the plurality and intensiveness of the incoming information [8; 9; 12]. Previous and concurrent efforts to raise public awareness with regards to the hazards involved in the inappropriate use of those technologies during driving have not managed to mitigate this issue [7].  
On our earlier work, it was deemed ideal to utilise the vast windshield area in front of the driver's FOV with the use of a head-up display (HUD) system. The latter reduces the gazing time in the infotainment devices typically positioned in the lower section of the dashboard (i.e., HDD) [1; 2; 12]. The idea to evolve the AR HUD interface concept and include a direct manipulation interface, based on a gesture recognition system stemmed from previous encouraging results. As such, the driver will not passively receive information and try to control them through the HDD buttons and touchscreens. The latter interaction with the HDD components defies the purpose or reduces the efficiency of a HUD system, as the driver is still required to take the eye-off-the-road and the hands off-the-steering-wheel.  
In contrast, the proposed system enables the driver to control the AR symbols through a novel gesture recognition user interface (UI) presented in earlier studies [4; 13]. The employment of a gesture recognition system that offers to the driver the ability to directly operate the AR symbols projected in the HUD section of the windshield significantly reduces the gazing time off-the-road [13]. For the evaluation of the system, we have utilised a full-scale, virtual reality (VR) driving simulator, which was customized to accommodate the proposed AR HUD interface. The simulation scenarios were based on real-life accidents which were replicated in the VR driving simulation environment. For this purpose, an instance of the digital twin city of Glasgow and the surrounding motorways was modelled to accommodate the scenarios, increase the immersion and the realism of the simulation. Thirty drivers performed the evaluation and the results are presented analytically in the following sections.