## 3 Interview Results
### Personalized Dialogue Needs of Drivers  
Drivers' personalized dialogue needs were analyzed in relation to their occupational type, driving scenarios, and fatigue status. Interview data revealed significant differences in dialogue preferences among different categories of drivers.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Selective Coding (Core Category)** & **Axial Coding (Subcategory)** & **Open Coding (Initial Concepts)** \\ \hline \multirow{6}{*}{Optimization of Voice Assistants} & \multirow{2}{*}{Needs by Fatigue Level} & Severe fatigue (strong stimuli), mild fatigue (light social interaction), no fatigue (minimal intervention) \\  & & Over-intervention, moderate reminders, demand-based adjustment \\ \hline \hline \end{tabular}
\end{table}
Table 3: _Cont._Long-haul truck drivers typically exhibited task-oriented dialogue needs, with a preference for highly interactive communication. For instance, P02 (a long-haul truck driver) stated, \"_During long-distance driving, what I need most is navigation and traffic updates, which help me stay focused_\". Similarly, P06 remarked, \"_When I'm driving for extended periods, having interactive Q&A--especially about the weather or road conditions--helps me relax a bit_\". These drivers rely on efficient information transmission during driving, and therefore prefer dialogues from voice assistants that are strongly task-focused, such as navigation and traffic information. Meanwhile, interactive elements help mitigate feelings of fatigue.  
Taxi and ride-hailing drivers showed a stronger preference for socially oriented dialogues. Their interactions with passengers often provided a source of relaxation and social engagement. For example, P10 (a taxi driver) commented, \"_Chutting with passengers makes driving feel less monotonous, especially during night shifts. The interaction helps me relax mentally_\". P17 (a ride-hailing driver) added, \"_Talking with passengers isn't just about customer service_--_it's social. That interaction helps reduce fatigue_\". For these drivers, especially during peak hours or nighttime driving, social dialogue serves to alleviate psychological fatigue and reduce the sense of isolation.  
Private car owners, in contrast, generally preferred more relaxed and entertainment-oriented dialogues. During commutes or short-distance trips, they tended to use voice assistants for casual conversations, music, or family-related communication. As P18 (a private car owner) noted, \"_I usually listen to music or news while driving--it helps me relax, especially during the morning rush. Music keeps me alert_\". Likewise, P21 shared, \"_I enjoy chatting with my family while driving, especially on long trips. The voice assistant helps me stay connected with them_\". Thus, private car owners' dialogue preferences tend to focus on entertainment, relaxation, and family communication, enabling emotional regulation and social connection.  
Drivers' personalized dialogue needs vary based on their professional background, driving conditions, and fatigue levels. Long-haul truck drivers benefit most from task-oriented and highly interactive dialogues to maintain alertness and reduce fatigue. Taxi and ride-hailing drivers seek social interaction to combat loneliness and psychological fatigue, while private car owners prioritize relaxed, entertainment-based, and family-centered dialogues to enhance comfort and emotional well-being during driving. Voice assistant systems should therefore be tailored to accommodate these differentiated needs to optimize the user experience and promote driving safety.