Enhancing the Driver’s Comprehension of ADS’s System Limitations: An HMI Providing Request-to-Intervene Trigger and Reason Explanation

Level 3 automated driving systems (ADS) have attracted significant attention and are being commercialized. A Level 3 ADS prompts the driver to take control by requesting to intervene (RtI) when its operational design domain (ODD) or system limitations are exceeded. However, complex traffic situations can cause drivers to perceive multiple potential triggers of RtI simultaneously, causing hesitation or confusion during take-over. Therefore, drivers need clearly understand the ADS's system limitations to ensure safe take-over. In this study, we propose a voice-based instructional HMI for providing RtI trigger cues and reason to help drivers understand ADS's system limitations. The results of a between-group experiment using a driving simulator showed that incorporating effective trigger cues and reason into the RtI enabled drivers to comprehend the ADS's system limitations better. Moreover, the vast majority of participants, instructed via the proposed method, could actively takeover control of the ADS in cases where RtI fails, thereby significantly reducing the probability of collisions. Therefore, using our proposed method to continually enhance the driver's understanding of the system limitations of ADS is crucial for promoting safer and more effective user interactions with ADS in real-time.