The effect of non-driving task takeover request message timing on novice drivers' driving trust

The unpredictable behavior patterns of self-driving vehicles in SAE level 3 autonomous driving can be untrustworthy to the driver. In self-driving vehicles, vehicle actions must be fed back to the user so that they are aware of the vehicle's actions. Otherwise, opaque information can lead to distrust of the vehicle by the driver. Flat-view displays (HUDs) provide an opportunity to visually and effectively inform drivers about vehicle perception and interpretation of the driving environment. Research has illustrated the importance of where and when HUD information is displayed. In "warning" situations, the timing of the display of necessary information can have a significant impact on driving safety; if warning messages are not properly placed or timed, drivers may have difficulty (or even fail to detect) the warning, thereby seriously endangering their safety and that of others. Drivers must detect and understand vehicle action messages when they are first displayed and turn their attention to the road as soon as possible so that they can take over the vehicle, react to potential hazards ahead or around them, and successfully avoid an accident. As a result, where/when the HUD is placed to display this dynamic information is critical; otherwise, the HUD's benefits will be negated. In this work, a driving experiment divided 26 participants into two groups (conservative drivers and novice drivers) and focused on the impact of HUD information presence timing on user experience and trust, measuring the impact of three HUD information presence timings (50m/70m/90m) on novice driver trust across four driving tasks (steer/stop/start/change lanes). The experimental setup was conducted in a simulated cockpit with a screen placed in front of the cockpit and a record of real driving displayed on a canvas screen. Subjects completed the User Experience Questionnaire (UEQ), the Trust Scale (TS), and the Preference for Overall Driving Experience (PREF) scale by watching a video. After completing the scales, user interviews were conducted to understand the reasons for the users' subjective preferences and other additional information. The results showed that the HUD message display enhanced the user experience and trust in the automated system. Significant differences were found in the timing of HUD messages by driving scenario as well as in preferences for the timing of HUD messages by driving style. The interaction of driving style with the driving environment and HUD complexity warrants further study. We present optimized design strategies for the timing of HUD information appearance based on the research.