## 4 Discussion
### Implications for Future Interior Design  
Automotive interiors are designed to support various activities of drivers and passengers while ensuring safety. As automation levels advance from L3 to L5, these changes are shaping the way car interiors are designed. Below, we explore the key implications for interior design based on the trends of NDRAs. **Group activities**: As passengers engage in social interactions, automotive interiors will need flexible seating arrangements. Studies show that a 140-degree seat angle is optimal for communication between passengers [54, 55]. However, privacy and safety remain important, especially when traveling with strangers [14, 56]. Although rotating seats enhance interaction, current safety standards address mainly frontal seating positions [57], making it challenging to ensure the safety of such seating configurations [58]. Therefore, interiors that support social interaction through adaptable seating layouts must balance passenger communication with privacy and safety, particularly in shared autonomous vehicles. **Smartphone usage**: With the increasing prevalence of smartphones and tablets, vehicle interiors should integrate dedicated spaces for these devices to enhance media usage [59]. Features like angled armrests [60] may be beneficial in supporting comfortable smartphone use, allowing passengers to engage with their devices more easily during travel. **Working with laptops**: As working becomes more common in higher levels of automation, vehicle interiors should be designed to accommodate laptop use. However, motion sickness remains a concern [61], though mitigation technologies are advancing [62]. laptops up to 3 kg are often used in vehicles, but there are usually no specific fixtures to secure them, posing potential safety risks in collisions, particularly given current standards that focus on frontal seating. Future interiors should incorporate stable surfaces or fixtures for laptops while also addressing the issue of motion sickness. **Sleeping:** Adapting the car interior to support sleeping is essential, especially for L4 and L5 cars. Although a small car space may not be as comfortable as a large bed, research indicates that sleeping in limited spaces is feasible [63, 64]. Since up to 70% of people prefer side sleeping [65], vehicle interiors should be designed to accommodate this common posture. Recent research indicates that a backrest with a 50\({}^{\circ}\) recline angle might be the most comfortable position for sleep [66], though this could pose safety challenges for passenger restraint systems design, as inclined seating increases the occurrence of submarining (sliding underneath the lap belt) in case of a crash [67]. Future interior designs of automated vehicles, particularly for L5, should prioritize reclining options for various sleeping positions while integrating safety features to mitigate these risks. **Personalization**: As automation advances, the variety of NDRAs increases, necessitating personalized and customizable car interiors for specific use cases [68, 69]. However, considering the lengthy certification processes involved in vehicle design and production, the feasibility of full personalization becomes questionable. It may be more practical to adopt a standardized approach with limited customization options that still cater to user preferences while ensuring compliance with safety regulations. Since cars are costly,long-term assets, creating personalized designs without diminishing their value presents a significant challenge. This trade-off between personalization and practicality will be central in shaping the future of vehicle designs. **Special user groups:** This study primarily focuses on NDRAs for adults, but elderly individuals, children, and special groups such as pregnant women, visually impaired people, and people with reduced mobility (PRM) may have different needs and activities in AVs. For example, [PERSON] et al. [70] suggest that AVs could lower the driving age limit, while [PERSON] et al.