## 5 Discussion
### The Necessity of Adaptive Voice Interaction  
With the continuous advancement of intelligent voice assistants and autonomous driving technology, the importance of adaptive voice interaction in reducing driving fatigue and enhancing driving safety has become increasingly prominent [53]. Based on SOR theory, a driver's fatigue state significantly influences their behavioral responses, and the interaction strategy of a voice assistant needs to dynamically adjust based on the driver's fatigue level, contextual demands, and individual preferences. The findings of this study show that when the interaction content and methods of the voice assistant can flexibly adapt to the driver's changing state, they are more effective in helping alleviate fatigue, improve alertness, and ultimately enhance driving safety.  
In severe fatigue states, a driver's cognitive function and emotional stability significantly decline, with slower reaction times and distracted attention [54]. At this point, the voice assistant should adopt a high-intensity dialogue strategy, such as humorous anecdotes or Q&A-style interactions, to provide emotional stimulation and cognitive awakening, quickly capture attention, and restore alertness. In contrast, mechanical, repetitive, or emotionally detached voice content often fails to have a positive effect and may even worsen the driver's fatigue, leading to negative emotional responses and cognitive breakdown. This further validates that interacting with the system helps significantly reduce driver fatigue and boredom [55].  
For mild fatigue states, although drivers exhibit initial signs of fatigue, their cognitive abilities remain relatively stable. In this situation, the voice assistant can use low-intensity, non-task-oriented, social dialogues, such as casual chats or informal greetings, to help the driver release stress, maintain a positive mood, and continue focusing on the road environment. This type of interaction reduces psychological load during driving while avoiding cognitive interference, helping delay fatigue development and enhancing driving continuity [56]. Studies have also shown that voice robots can enhance drivers' sense of safety and calmness through engagement and emotional regulation during simulated driving [57] and improve alertness in autonomous driving through active listening and voice reminders [58].  
In a non-fatigued state, the voice assistant's intervention should be minimized. Excessive voice prompts or irrelevant interactions may interrupt the driver's focus on the current traffic environment, leading to distraction or cognitive load, thereby affecting driving performance. Therefore, the voice assistant should avoid unnecessary interventions unless the driver initiates communication. In this state, voice interaction should be task-oriented and concise, assisting the driver in focusing on the driving task [59].  
Beyond fatigue states, a driver's personalized needs are also an important variable in designing voice assistant interaction strategies. Factors such as the voice assistant's voice characteristics, tone, gender, and privacy protection mechanisms significantly influence its acceptance [60]. Different occupational groups exhibit varying driving behaviors and interaction needs, requiring differentiated designs. For instance, long-haul freight drivers prefer task-oriented voice support, such as real-time traffic information and navigation prompts; taxi drivers are more sensitive to passenger-related interactions and may prioritize the voice assistant's social and contextual awareness; while private car owners tend to prefer light, entertainment-oriented dialogues to alleviate driving pressure and fatigue. These differences suggest that future voice interaction systems should enhance their ability to recognize and respond to the emotional states and personalized needs of drivers, achieving truly dynamic adaptation and intelligent collaboration, thus ensuring safety while improving the user experience.